fix c++17 check

#393

Appearantly there are compilers that support -std=c++17 but do not
really support c++17.

(cherry picked from commit 9921136)

Author: Mic92

configure.ac

@@ -41,12 +41,5 @@ AC_ARG_WITH([ubsan],
 )
 AM_CONDITIONAL([WITH_UBSAN], [test x"$with_ubsan" = xyes])
 
-CPLUSPLUS=
-AX_CHECK_COMPILE_FLAG([-std=c++17], [CPLUSPLUS=17], [], [$WERROR])
-
-if test -z "$CPLUSPLUS"; then
-  AC_MSG_ERROR([Your compiler does not have the necessary C++17 support! Cannot proceed.])
-fi
-
 AC_CONFIG_FILES([Makefile src/Makefile tests/Makefile patchelf.spec])
 AC_OUTPUT