stm32: common: Fix STM32_TARGET_TRIPLET

cmake/stm32/common.cmake

@@ -34,8 +34,14 @@ if(NOT STM32_TOOLCHAIN_PATH)
 endif()
 
 if(NOT STM32_TARGET_TRIPLET)
-    set(STM32_TARGET_TRIPLET "arm-none-eabi")
-    message(STATUS "No STM32_TARGET_TRIPLET specified, using default: " ${STM32_TARGET_TRIPLET})
+    if(DEFINED ENV{STM32_TARGET_TRIPLET})
+        message(STATUS "Detected toolchain path STM32_TARGET_TRIPLET in environmental variables: ")
+        message(STATUS "$ENV{STM32_TARGET_TRIPLET}")
+        set(STM32_TARGET_TRIPLET $ENV{STM32_TARGET_TRIPLET})
+    else()
+        set(STM32_TARGET_TRIPLET "arm-none-eabi")
+        message(STATUS "No STM32_TARGET_TRIPLET specified, using default: " ${STM32_TARGET_TRIPLET})
+    endif()
 endif()
 
 set(CMAKE_SYSTEM_NAME Generic)