Respect linking order of libraries for PlatformIO (#8263)

* Respect linking order of libraries

Now has the same order as the Arduino IDE does with its platform.txt

* Remove double-referenced libs

* Change implementation style

Instead of injecting at magic indices, which might break when some other extra-scripts inject other libraries, let's create the LIBS array at the bottom in easy to understand and correct order.

tools/platformio-build.py

@@ -139,12 +139,8 @@ def scons_patched_match_splitext(path, suffixes=None):
         join(FRAMEWORK_DIR, "tools", "sdk", "ld")
     ],
 
-    # A list of one or more libraries that will be linked with any executable programs created by this environment
-    LIBS=[
-        "hal", "phy", "pp", "net80211", "wpa", "crypto", "main",
-        "wps", "bearssl", "espnow", "smartconfig", "airkiss", "wpa2",
-        "m", "c", "gcc"
-    ],
+    # LIBS is set at the bottom of the builder script
+    # where we know about all system libraries to be included
 
     LIBSOURCE_DIRS=[
         join(FRAMEWORK_DIR, "libraries")
@@ -218,43 +214,44 @@ def scons_patched_match_splitext(path, suffixes=None):
 #
 # lwIP
 #
+lwip_lib = None
 if "PIO_FRAMEWORK_ARDUINO_LWIP2_IPV6_LOW_MEMORY" in flatten_cppdefines:
     env.Append(
         CPPDEFINES=[("TCP_MSS", 536), ("LWIP_FEATURES", 1), ("LWIP_IPV6", 1)],
         CPPPATH=[join(FRAMEWORK_DIR, "tools", "sdk", "lwip2", "include")],
-        LIBS=["lwip6-536-feat"]
     )
+    lwip_lib = "lwip6-536-feat"
 elif "PIO_FRAMEWORK_ARDUINO_LWIP2_IPV6_HIGHER_BANDWIDTH" in flatten_cppdefines:
     env.Append(
         CPPDEFINES=[("TCP_MSS", 1460), ("LWIP_FEATURES", 1), ("LWIP_IPV6", 1)],
         CPPPATH=[join(FRAMEWORK_DIR, "tools", "sdk", "lwip2", "include")],
-        LIBS=["lwip6-1460-feat"]
     )
+    lwip_lib = "lwip6-1460-feat"
 elif "PIO_FRAMEWORK_ARDUINO_LWIP2_HIGHER_BANDWIDTH" in flatten_cppdefines:
     env.Append(
         CPPDEFINES=[("TCP_MSS", 1460), ("LWIP_FEATURES", 1), ("LWIP_IPV6", 0)],
         CPPPATH=[join(FRAMEWORK_DIR, "tools", "sdk", "lwip2", "include")],
-        LIBS=["lwip2-1460-feat"]
     )
+    lwip_lib = "lwip2-1460-feat"
 elif "PIO_FRAMEWORK_ARDUINO_LWIP2_LOW_MEMORY_LOW_FLASH" in flatten_cppdefines:
     env.Append(
         CPPDEFINES=[("TCP_MSS", 536), ("LWIP_FEATURES", 0), ("LWIP_IPV6", 0)],
         CPPPATH=[join(FRAMEWORK_DIR, "tools", "sdk", "lwip2", "include")],
-        LIBS=["lwip2-536"]
     )
+    lwip_lib = "lwip2-536"
 elif "PIO_FRAMEWORK_ARDUINO_LWIP2_HIGHER_BANDWIDTH_LOW_FLASH" in flatten_cppdefines:
     env.Append(
         CPPDEFINES=[("TCP_MSS", 1460), ("LWIP_FEATURES", 0), ("LWIP_IPV6", 0)],
         CPPPATH=[join(FRAMEWORK_DIR, "tools", "sdk", "lwip2", "include")],
-        LIBS=["lwip2-1460"]
     )
+    lwip_lib = "lwip2-1460"
 # PIO_FRAMEWORK_ARDUINO_LWIP2_LOW_MEMORY (default)
 else:
     env.Append(
         CPPDEFINES=[("TCP_MSS", 536), ("LWIP_FEATURES", 1), ("LWIP_IPV6", 0)],
         CPPPATH=[join(FRAMEWORK_DIR, "tools", "sdk", "lwip2", "include")],
-        LIBS=["lwip2-536-feat"]
     )
+    lwip_lib = "lwip2-536-feat"
 
 #
 # Waveform
@@ -266,17 +263,17 @@ def scons_patched_match_splitext(path, suffixes=None):
 #
 # Exceptions
 #
+stdcpp_lib = None
 if "PIO_FRAMEWORK_ARDUINO_ENABLE_EXCEPTIONS" in flatten_cppdefines:
     env.Append(
         CXXFLAGS=["-fexceptions"],
-        LIBS=["stdc++-exc"]
     )
+    stdcpp_lib = "stdc++-exc"
 else:
     env.Append(
         CXXFLAGS=["-fno-exceptions"],
-        LIBS=["stdc++"]
     )
-
+    stdcpp_lib = "stdc++"
 #
 # VTables
 #
@@ -355,6 +352,15 @@ def scons_patched_match_splitext(path, suffixes=None):
 assert mmu_flags
 env.Append(CPPDEFINES=mmu_flags)
 
+# A list of one or more libraries that will be linked with any executable programs created by this environment
+# We do this at this point so that we can put the libraries in their correct order more easily
+env.Append(
+    LIBS=[
+        "hal", "phy", "pp", "net80211", lwip_lib, "wpa", "crypto", "main",
+        "wps", "bearssl", "espnow", "smartconfig", "airkiss", "wpa2",
+        stdcpp_lib, "m", "c", "gcc"
+    ]
+)
 
 # Build the eagle.app.v6.common.ld linker file
 app_ld = env.Command(