[bsp] [stm32] stm32f7支持c++环境

编译报错
Warning: L6330W: Undefined symbol SHT$$INIT_ARRAY$$Base (referred from crt_init.o). Unused section has been removed.
Warning: L6330W: Undefined symbol SHT$$INIT_ARRAY$$Limit (referred from crt_init.o). Unused section has been removed.

bsp/stm32/stm32f767-fire-challenger/rtconfig.py

@@ -34,6 +34,7 @@ if PLATFORM == 'gcc':
     # toolchains
     PREFIX = 'arm-none-eabi-'
     CC = PREFIX + 'gcc'
+    CXX = PREFIX + 'g++'
     AS = PREFIX + 'gcc'
     AR = PREFIX + 'ar'
     CXX = PREFIX + 'g++'
@@ -42,6 +43,7 @@ if PLATFORM == 'gcc':
     SIZE = PREFIX + 'size'
     OBJDUMP = PREFIX + 'objdump'
     OBJCPY = PREFIX + 'objcopy'
+    STRIP = PREFIX + 'strip'
 
     DEVICE = ' -mcpu=cortex-m7 -mthumb -mfpu=fpv5-d16 -mfloat-abi=hard -ffunction-sections -fdata-sections'
     CFLAGS = DEVICE + ' -std=c99 -Dgcc'
@@ -59,9 +61,18 @@ if PLATFORM == 'gcc':
 
     POST_ACTION = OBJCPY + ' -O binary $TARGET rtthread.bin\n' + SIZE + ' $TARGET \n'
 
+    # module setting 
+    CXXFLAGS = ' -Woverloaded-virtual -fno-exceptions -fno-rtti '
+    M_CFLAGS = CFLAGS + ' -mlong-calls -fPIC '
+    M_CXXFLAGS = CXXFLAGS + ' -mlong-calls -fPIC'
+    M_LFLAGS = DEVICE + CXXFLAGS + ' -Wl,--gc-sections,-z,max-page-size=0x4' +\
+                                    ' -shared -fPIC -nostartfiles -static-libgcc'
+    M_POST_ACTION = STRIP + ' -R .hash $TARGET\n' + SIZE + ' $TARGET \n'
+
 elif PLATFORM == 'armcc':
     # toolchains
     CC = 'armcc'
+    CXX = 'armcc'
     AS = 'armasm'
     AR = 'armar'
     LINK = 'armlink'
@@ -91,6 +102,7 @@ elif PLATFORM == 'armcc':
 elif PLATFORM == 'iar':
     # toolchains
     CC = 'iccarm'
+    CXX = 'iccarm'
     AS = 'iasmarm'
     AR = 'iarchive'
     LINK = 'ilinkarm'
@@ -131,5 +143,7 @@ elif PLATFORM == 'iar':
     LFLAGS = ' --config "board/linker_scripts/link.icf"'
     LFLAGS += ' --entry __iar_program_start'
 
+    CXXFLAGS = CFLAGS
+
     EXEC_PATH = EXEC_PATH + '/arm/bin/'
     POST_ACTION = 'ielftool --bin $TARGET rtthread.bin'