try fix #6

Author: Extravert-ir

sdk/cmake/gcc.cmake

@@ -53,7 +53,7 @@ if(NOT CMAKE_C_COMPILER_ID STREQUAL "Clang")
         add_compile_options("$<$<COMPILE_LANGUAGE:C>:-Wold-style-declaration>")
     endif()
 else()
-    add_compile_options("$<$<COMPILE_LANGUAGE:C>:-std=gnu99;-Wno-microsoft>")
+    add_compile_options("$<$<COMPILE_LANGUAGE:C>:-Wno-microsoft>")
     add_compile_options(-Wno-pragma-pack)
     add_compile_options(-fno-associative-math)
     add_compile_options(-fcommon)