cmake/compiler: Add linker_script compiler property

This property specifies the flag used to pass the linker script filename
through the compiler front end tot he linker.

For clang, we use the general purpose linker-pass through -Wl flag with -T:
-Wl,-T as clang doesn't support -T.

For gcc, we use -T directly as this keeps the picolibc specs file from
inserting the picolibc linker script as well.

If the compiler doesn't specify a value, we continue to use -Wl,-T as
before.

Signed-off-by: Keith Packard <keithp@keithp.com>

CMakeLists.txt

@@ -485,8 +485,9 @@ if(CONFIG_USERSPACE)
 endif()
 
 get_property(TOPT GLOBAL PROPERTY TOPT)
-set_ifndef(  TOPT -Wl,-T) # clang doesn't pick -T for some reason and complains,
-                          # while -Wl,-T works for both, gcc and clang
+get_property(COMPILER_TOPT TARGET compiler PROPERTY linker_script)
+set_ifndef(  TOPT "${COMPILER_TOPT}")
+set_ifndef(  TOPT -Wl,-T) # Use this if the compiler driver doesn't set a value
 
 if(CONFIG_HAVE_CUSTOM_LINKER_SCRIPT)
   set(LINKER_SCRIPT ${APPLICATION_SOURCE_DIR}/${CONFIG_CUSTOM_LINKER_SCRIPT})

cmake/compiler/clang/compiler_flags.cmake

@@ -23,6 +23,9 @@ set_compiler_property(PROPERTY diagnostic -fcolor-diagnostics)
 # clang flag to save temporary object files
 set_compiler_property(PROPERTY save_temps -save-temps)
 
+# clang doesn't handle the -T flag
+set_compiler_property(PROPERTY linker_script -Wl,-T)
+
 #######################################################
 # This section covers flags related to warning levels #
 #######################################################

cmake/compiler/compiler_flags_template.cmake

@@ -106,6 +106,9 @@ set_compiler_property(PROPERTY debug)
 # Flags to save temporary object files
 set_compiler_property(PROPERTY save_temps)
 
+# Flag to specify linker script
+set_compiler_property(PROPERTY linker_script)
+
 set_compiler_property(PROPERTY no_common)
 
 # Flags for imacros. The specific header must be appended by user.

cmake/compiler/gcc/compiler_flags.cmake

@@ -182,6 +182,9 @@ set_compiler_property(PROPERTY debug -g)
 # Flags to save temporary object files
 set_compiler_property(PROPERTY save_temps -save-temps=obj)
 
+# Flag to specify linker script
+set_compiler_property(PROPERTY linker_script -T)
+
 # Flags to not track macro expansion
 set_compiler_property(PROPERTY no_track_macro_expansion -ftrack-macro-expansion=0)