build system: don't add GCC-specific options when building with clang

CMakeLists.txt

@@ -90,6 +90,13 @@ if(CONFIG_COMPILER_DUMP_RTL_FILES)
     list(APPEND compile_options "-fdump-rtl-expand")
 endif()
 
+# GCC-specific options
+if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    list(APPEND compile_options "-fstrict-volatile-bitfields"
+                                "-Wno-error=unused-but-set-variable"
+                                )
+endif()
+
 list(APPEND link_options "-fno-lto")
 
 idf_build_set_property(COMPILE_OPTIONS "${compile_options}" APPEND)

examples/build_system/cmake/linux_host_app/sdkconfig.defaults

@@ -1,2 +1,2 @@
 CONFIG_IDF_TARGET="linux"
-CONFIG_CXX_EXCEPTIONS=y
+CONFIG_COMPILER_CXX_EXCEPTIONS=y

tools/cmake/build.cmake

@@ -94,12 +94,10 @@ function(__build_set_default_build_specifications)
 
     list(APPEND compile_options     "-ffunction-sections"
                                     "-fdata-sections"
-                                    "-fstrict-volatile-bitfields"
                                     # warning-related flags
                                     "-Wall"
                                     "-Werror=all"
                                     "-Wno-error=unused-function"
-                                    "-Wno-error=unused-but-set-variable"
                                     "-Wno-error=unused-variable"
                                     "-Wno-error=deprecated-declarations"
                                     "-Wextra"

tools/cmake/project.cmake

@@ -460,8 +460,10 @@ macro(project project_name)
     endif()
     target_link_libraries(${project_elf} ${build_components})
 
-    set(mapfile "${CMAKE_BINARY_DIR}/${CMAKE_PROJECT_NAME}.map")
-    target_link_libraries(${project_elf} "-Wl,--cref -Wl,--Map=${mapfile}")
+    if(CMAKE_C_COMPILER_ID STREQUAL "GNU")
+        set(mapfile "${CMAKE_BINARY_DIR}/${CMAKE_PROJECT_NAME}.map")
+        target_link_libraries(${project_elf} "-Wl,--cref -Wl,--Map=${mapfile}")
+    endif()
 
     set_property(DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}" APPEND PROPERTY
         ADDITIONAL_MAKE_CLEAN_FILES

tools/cmake/toolchain-linux.cmake

@@ -1,8 +1,3 @@
-set(CMAKE_SYSTEM_NAME Generic)
-
-set(CMAKE_C_COMPILER gcc)
-set(CMAKE_CXX_COMPILER g++)
-set(CMAKE_ASM_COMPILER gcc)
-
-set(CMAKE_C_FLAGS "-Wno-frame-address" CACHE STRING "C Compiler Base Flags")
-set(CMAKE_CXX_FLAGS "-Wno-frame-address" CACHE STRING "C++ Compiler Base Flags")
+# The build system assumes that toolchain-${IDF_TARGET}.cmake file
+# is present. It is not necessary for the host build, so we keep
+# this file as a placeholder.