Attempt 2

src/libraries/Native/Unix/configure.cmake

@@ -56,19 +56,19 @@ if(CLR_CMAKE_USE_SYSTEM_LIBUNWIND)
     # just check and igore the variable.
 endif()
 
-# We compile with -Werror, so we need to make sure these code fragments compile without warnings.
-# Older CMake versions (3.8) do not assign the result of their tests, causing unused-value errors
-# which are not distinguished from the test failing. So no error for that one.
-# For clang-5.0 avoid errors like "unused variable 'err' [-Werror,-Wunused-variable]".
-set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror -Wno-error=unused-value -Wno-error=unused-variable")
+# We don't want to use deprecated APIs
+check_c_compiler_flag("-Wdeprecated-declarations" "C_SUPPORTS_DEPRECATED_DECLARATIONS")
+if(C_SUPPORTS_DEPRECATED_DECLARATIONS)
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror=deprecated-declarations")
+endif()
 
 # Apple platforms like macOS/iOS allow targeting older operating system versions with a single SDK,
 # the mere presence of a symbol in the SDK doesn't tell us whether the deployment target really supports it.
 # The compiler raises a warning when using an unsupported API, turn that into an error so check_symbol_exists()
 # can correctly identify whether the API is supported on the target.
 check_c_compiler_flag("-Wunguarded-availability" "C_SUPPORTS_WUNGUARDED_AVAILABILITY")
 if(C_SUPPORTS_WUNGUARDED_AVAILABILITY)
-  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Wunguarded-availability")
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -Werror=unguarded-availability")
 endif()
 
 # in_pktinfo: Find whether this struct exists
@@ -671,7 +671,16 @@ check_symbol_exists(
     time.h
     HAVE_CLOCK_GETTIME_NSEC_NP)
 
-check_library_exists(pthread pthread_condattr_setclock "" HAVE_PTHREAD_CONDATTR_SETCLOCK)
+check_library_exists(pthread pthread_create "" HAVE_LIBPTHREAD)
+check_library_exists(c pthread_create "" HAVE_PTHREAD_IN_LIBC)
+
+if (HAVE_LIBPTHREAD)
+  set(PTHREAD_LIBRARY pthread)
+elseif (HAVE_PTHREAD_IN_LIBC)
+  set(PTHREAD_LIBRARY c)
+endif()
+
+check_library_exists(${PTHREAD_LIBRARY} pthread_condattr_setclock "" HAVE_PTHREAD_CONDATTR_SETCLOCK)
 
 check_symbol_exists(
     futimes