Modify individual file caching in FindSTM32HAL by first converting to C identifier.

This makes sure we've got a safe name for a variable.

cmake/FindSTM32HAL.cmake

@@ -205,13 +205,14 @@ FIND_PATH(STM32HAL_INCLUDE_DIR ${HAL_HEADERS}
 )
 
 FOREACH(HAL_SRC ${HAL_SRCS})
-    SET(HAL_${HAL_SRC}_FILE HAL_SRC_FILE-NOTFOUND)
-    FIND_FILE(HAL_${HAL_SRC}_FILE ${HAL_SRC}
+    STRING(MAKE_C_IDENTIFIER "${HAL_SRC}" HAL_SRC_CLEAN)
+    SET(HAL_${HAL_SRC_CLEAN}_FILE HAL_SRC_FILE-NOTFOUND)
+    FIND_FILE(HAL_${HAL_SRC_CLEAN}_FILE ${HAL_SRC}
         PATH_SUFFIXES src stm32${STM32_FAMILY_LOWER}
         HINTS ${STM32Cube_DIR}/Drivers/STM32${STM32_FAMILY}xx_HAL_Driver/Src
         CMAKE_FIND_ROOT_PATH_BOTH
     )
-    LIST(APPEND STM32HAL_SOURCES ${HAL_${HAL_SRC}_FILE})
+    LIST(APPEND STM32HAL_SOURCES ${HAL_${HAL_SRC_CLEAN}_FILE})
 ENDFOREACH()
 
 INCLUDE(FindPackageHandleStandardArgs)