wasm-mutator-fuzz: Set compilers earlier (#3585)

CMAKE_C_COMPILER etc should be set before project(),
in which cmake tries to decide which compiler to use.

tests/fuzz/wasm-mutator-fuzz/CMakeLists.txt

@@ -3,10 +3,6 @@
 
 cmake_minimum_required (VERSION 2.8)
 
-project(wasm_mutator)
-
-set (CMAKE_BUILD_TYPE Debug)
-
 if (NOT DEFINED CMAKE_C_COMPILER)
 set (CMAKE_C_COMPILER "clang")
 endif ()
@@ -14,6 +10,10 @@ if (NOT DEFINED CMAKE_CXX_COMPILER)
 set (CMAKE_CXX_COMPILER "clang++")
 endif ()
 
+project(wasm_mutator)
+
+set (CMAKE_BUILD_TYPE Debug)
+
 string (TOLOWER ${CMAKE_HOST_SYSTEM_NAME} WAMR_BUILD_PLATFORM)
 
 # Reset default linker flags