[PROF-9226] Add test for Ruby profiler when extension dir is moved an…

…d relative rpath is needed

**What does this PR do?**

This PR adds a new test case that validates that
DataDog/dd-trace-rb#3582 and
DataDog/dd-trace-rb#3683 keep working fine.

**Motivation:**

As described in DataDog/dd-trace-rb#3683, this
a somewhat annoying thing to test, but important to avoid regressing.

**Additional Notes:**

You can actually see the evolution of both of those fixes in
this test.

E.g. here's dd-trace-rb 1.21.0 (prior to
DataDog/dd-trace-rb#3582 ):

```
W, [2024-06-12T09:34:08.759519 #7]  WARN -- ddtrace: [ddtrace] (/app/vendor-moved/bundle/ruby/3.3.0/gems/ddtrace-1.21.1/lib/datadog/core/configuration/components.rb:115:in `startup!') Profiling was requested but is not supported, profiling disabled: There was an error loading the profiling native extension due to 'RuntimeError Failure to load datadog_profiling_native_extension.3.3.2_x86_64-linux due to /app/vendor-moved/bundle/ruby/3.3.0/gems/ddtrace-1.21.1/lib/datadog/profiling/../../datadog_profiling_native_extension.3.3.2_x86_64-linux.so: cannot open shared object file: No such file or directory' at '/app/vendor-moved/bundle/ruby/3.3.0/gems/ddtrace-1.21.1/lib/datadog/profiling/load_native_extension.rb:26:in `<top (required)>''
    --- FAIL: TestScenarios/scenarios/ruby_extension_dir_and_rpath (14.86s)
```

in this version, we failed because we couldn't load the native
extension.

Then here's dd-trace-rb 1.23.1 (without
DataDog/dd-trace-rb#3683 ) and if we
don't move the `vendor` folder (but still delete the so from the
lib folder):

```
    --- PASS: TestScenarios/scenarios/ruby_extension_dir_and_rpath (18.96s)
```

...but if we additionally move the vendor folder (aka what this PR
does in the Dockerfile):

```
W, [2024-06-12T09:37:33.517188 #6]  WARN -- ddtrace: [ddtrace] (/app/vendor-moved/bundle/ruby/3.3.0/gems/ddtrace-1.23.1/lib/datadog/core/configuration/components.rb:116:in `startup!') Profiling was requested but is not supported, profiling disabled: There was an error loading the profiling native extension due to 'RuntimeError Failure to load datadog_profiling_native_extension.3.3.2_x86_64-linux due to libdatadog_profiling.so: cannot open shared object file: No such file or directory' at '/app/vendor-moved/bundle/ruby/3.3.0/gems/ddtrace-1.23.1/lib/datadog/profiling/load_native_extension.rb:39:in `<top (required)>''
    --- FAIL: TestScenarios/scenarios/ruby_extension_dir_and_rpath (3.25s)
```

Notice it fails BUT the error is now different from the one above --
the error is relating to loading `libdatadog_profiling.so`, not
`datadog_profiling_native_extension.3.3.2_x86_64-linux.so`.

And with the change in DataDog/dd-trace-rb#3683
(which will be in 1.23.2):

```
    --- PASS: TestScenarios/scenarios/ruby_extension_dir_and_rpath (9.60s)
```

**NOTE**: For this test, unlike other Ruby tests we have, we're pulling
in the latest **released** gem version (e.g. with `gem 'datadog'` on the
`gems.rb` file), not the latest from git (as we do for other Ruby
tests).

This is because gems get installed in different paths when bundler
downloads them directly from git, and we want to validate the path when
a stable version is installed.

This also means that this PR will show up as failed until the latest
datadog release (which will be 2.2.0) gets released. (Or 1.23.2, but
I left the test setup to test the latest 2.x releases, not the 1.x ones,
although I used 1.x on my tests above to show the evolution of the
issue).

.gitignore

@@ -1,6 +1,8 @@
 #==============================================================================#
 # Directories to ignore (do not add trailing '/'s, they skip symlinks).
 #==============================================================================#
+binaries/*
 data/*
+
 .idea
-binaries/*
+gems.locked

scenarios/ruby_extension_dir_and_rpath/Dockerfile

@@ -0,0 +1,20 @@
+FROM ruby:3.3
+
+ENV DD_TRACE_DEBUG true
+ENV DD_PROFILING_PPROF_PREFIX="/app/data/profiles_"
+
+# Copy the Ruby program into the container
+COPY ./scenarios/ruby_extension_dir_and_rpath/gems.rb ./scenarios/ruby_basic/main.rb /app/
+RUN chmod 644 /app/*
+
+# Set the working directory to the location of the program
+WORKDIR /app
+
+RUN bundle config set --local path 'vendor/bundle'
+RUN bundle install
+RUN rm -f vendor/bundle/ruby/*/gems/ddtrace-*/lib/*so vendor/bundle/ruby/*/bundler/gems/*/lib/datadog*so
+RUN bundle config set --local path 'vendor-moved/bundle'
+RUN mv vendor vendor-moved
+
+# Run the program when the container starts
+CMD bundle exec ddprofrb exec ruby main.rb

scenarios/ruby_extension_dir_and_rpath/expected_profile.json

@@ -0,0 +1,23 @@
+{
+  "test_name":"ruby_basic",
+  "stacks": [
+    {
+      "profile-type": "cpu-time",
+      "stack-content":
+      [
+        {
+          "regular_expression": "\u003cmain\u003e;a",
+          "value": 330000000,
+          "percent": 33,
+          "error_margin": 7
+        },
+        {
+          "regular_expression": "\u003cmain\u003e;b",
+          "value": 660000000,
+          "percent": 66,
+          "error_margin": 7
+        }
+      ]
+    }
+  ]
+}

scenarios/ruby_extension_dir_and_rpath/gems.rb

@@ -0,0 +1,3 @@
+source 'https://rubygems.org'
+
+gem 'datadog'

scenarios/ruby_extension_dir_and_rpath/main.rb

@@ -0,0 +1,57 @@
+require 'timeout'
+
+# The Ruby profiler does not (yet) include a way of exporting a pprof to a file, so we implement it here:
+class ExportToFile
+  PPROF_PREFIX = ENV.fetch('DD_PROFILING_PPROF_PREFIX')
+
+  def export(flush)
+    File.write("#{PPROF_PREFIX}#{flush.start.strftime('%Y%m%dT%H%M%SZ')}.pprof", flush.pprof_data)
+    true
+  end
+end
+
+Datadog.configure do |c|
+  c.profiling.enabled = true
+  c.profiling.exporter.transport = ExportToFile.new
+end
+
+Timeout.timeout(5) do
+  until Datadog::Profiling::Collectors::CpuAndWallTimeWorker::Testing._native_is_running?(
+    Datadog.send(:components).profiler.send(:worker)
+  )
+    sleep(0.5)
+  end
+end
+
+def a
+  x = 0
+  i = 0
+  while i < 10_000_000
+    x += i
+    i += 1
+  end
+end
+
+def b
+  x = 0
+  i = 0
+  while i < 20_000_000
+    x += i
+    i += 1
+  end
+end
+
+test_duration = 50
+exec_time_env = ENV['EXECUTION_TIME_SEC']
+if exec_time_env
+  test_duration = exec_time_env.to_i
+  exit(1) if test_duration == 0
+end
+
+puts "Executable #{__FILE__} starting for #{test_duration} seconds"
+end_time = Time.now + test_duration
+while Time.now < end_time
+  a
+  b
+end
+puts "Executable #{__FILE__} finished successfully"