only add -Wno-potentially-evaluated-expression if compiler understand…

…s it

configure.ac

@@ -197,8 +197,10 @@ if eval "test x$enable_multithreading != xno"; then
 fi
 AC_SUBST(ENABLE_PARALLEL_TILE_DECODING)
 
-CXXFLAGS="$CXXFLAGS -Wall -Werror -Wsign-compare -Wconversion -Wno-sign-conversion -Wno-error=conversion -Wno-error=unused-parameter -Wno-potentially-evaluated-expression"
-CFLAGS="$CFLAGS -Wall -Werror -Wsign-compare -Wconversion -Wno-sign-conversion -Wno-error=conversion -Wno-error=unused-parameter -Wno-potentially-evaluated-expression"
+AC_C_CXX_COMPILE_FLAGS([-Wno-potentially-evaluated-expression])
+
+CXXFLAGS="$CXXFLAGS -Wall -Werror -Wsign-compare -Wconversion -Wno-sign-conversion -Wno-error=conversion -Wno-error=unused-parameter"
+CFLAGS="$CFLAGS -Wall -Werror -Wsign-compare -Wconversion -Wno-sign-conversion -Wno-error=conversion -Wno-error=unused-parameter"
 
 AC_MSG_NOTICE([---------------------------------------])
 AC_MSG_NOTICE([Multithreading: $enable_multithreading])

m4/ac_c_cxx_compile_flags.m4

@@ -0,0 +1,16 @@
+AC_DEFUN([AC_C_CXX_COMPILE_FLAGS],[
+NEW_CFLAGS="$CFLAGS"
+for ac_flag in $1
+do
+ AC_MSG_CHECKING(whether compiler supports $ac_flag)
+ CFLAGS="$NEW_CFLAGS $ac_flag"
+ AC_TRY_COMPILE(,[
+  void f() {};
+ ],[
+  NEW_CFLAGS="$CFLAGS"
+  AC_MSG_RESULT(yes)
+ ],AC_MSG_RESULT(no))
+done
+CFLAGS="$NEW_CFLAGS"
+CXXFLAGS="$NEW_CFLAGS"
+])