Add support for calling a function before main()

Also added a test for this feature (MBED_A22).
Fixes PRMBED-906.

Author: Bogdan Marinescu

workspace_tools/tests.py

@@ -203,6 +203,12 @@
         "dependencies": [MBED_LIBRARIES, TEST_MBED_LIB],
         "peripherals": ["digital_loop"]
     },
+    {
+        "id": "MBED_A22", "description": "Call function before main (mbed_main)",
+        "source_dir": join(TEST_DIR, "mbed", "call_before_main"),
+        "dependencies": [MBED_LIBRARIES, TEST_MBED_LIB],
+        "automated": True,
+    },
 
     # Size benchmarks
     {

workspace_tools/toolchains/gcc.py

@@ -64,7 +64,7 @@ def __init__(self, target, options=None, notify=None, tool_path=""):
         self.cc  = [join(tool_path, "arm-none-eabi-gcc"), "-std=gnu99"] + common_flags
         self.cppc =[join(tool_path, "arm-none-eabi-g++"), "-std=gnu++98"] + common_flags
 
-        self.ld = [join(tool_path, "arm-none-eabi-gcc"), "-Wl,--gc-sections"] + self.cpu
+        self.ld = [join(tool_path, "arm-none-eabi-gcc"), "-Wl,--gc-sections", "-Wl,--wrap,main"] + self.cpu
         self.sys_libs = ["stdc++", "supc++", "m", "c", "gcc"]
 
         self.ar = join(tool_path, "arm-none-eabi-ar")