fix the STM32_TOOLCHAIN_PATH not taken into account from env vars

cmake/stm32/common.cmake

@@ -18,15 +18,16 @@ if(NOT STM32_TOOLCHAIN_PATH)
         message(STATUS "Detected toolchain path STM32_TOOLCHAIN_PATH in environmental variables: ")
         message(STATUS "$ENV{STM32_TOOLCHAIN_PATH}")
         set(STM32_TOOLCHAIN_PATH $ENV{STM32_TOOLCHAIN_PATH})
-    endif()
-    if(NOT CMAKE_C_COMPILER)
-        set(STM32_TOOLCHAIN_PATH "/usr")
-        message(STATUS "No STM32_TOOLCHAIN_PATH specified, using default: " ${STM32_TOOLCHAIN_PATH})
     else()
-        # keep only directory of compiler
-        get_filename_component(STM32_TOOLCHAIN_PATH ${CMAKE_C_COMPILER} DIRECTORY)
-        # remove the last /bin directory
-        get_filename_component(STM32_TOOLCHAIN_PATH ${STM32_TOOLCHAIN_PATH} DIRECTORY)
+        if(NOT CMAKE_C_COMPILER)
+            set(STM32_TOOLCHAIN_PATH "/usr")
+            message(STATUS "No STM32_TOOLCHAIN_PATH specified, using default: " ${STM32_TOOLCHAIN_PATH})
+        else()
+            # keep only directory of compiler
+            get_filename_component(STM32_TOOLCHAIN_PATH ${CMAKE_C_COMPILER} DIRECTORY)
+            # remove the last /bin directory
+            get_filename_component(STM32_TOOLCHAIN_PATH ${STM32_TOOLCHAIN_PATH} DIRECTORY)
+        endif()
     endif()
     file(TO_CMAKE_PATH "${STM32_TOOLCHAIN_PATH}" STM32_TOOLCHAIN_PATH)
 endif()