cswrap-util: black-list conftest.adb used by autoconf

This fixes the following failure while scanning gcc-4.8.5-36.el7_6.2:

checking for gnatbind... gnatbind
checking for gnatmake... gnatmake
checking whether compiler driver understands Ada... no
checking how to compare bootstrapped objects... cmp --ignore-initial=16 $$f1 $$f2
checking for objdir... .libs
checking for the correct version of gmp.h... yes
checking for the correct version of mpfr.h... yes
checking for the correct version of mpc.h... yes
checking for the correct version of the gmp/mpfr/mpc libraries... yes
checking for version 0.10 of ISL... no
checking for version 0.11 of ISL... yes
checking for version 0.17.0 of CLooG... no
checking for version 0.18.0 of CLooG... yes
 'c++' language required by 'go' in stage 1; enabling
configure: error: GNAT is required to build ada

cswrap-util.c

@@ -109,7 +109,7 @@ bool remove_self_from_path(const char *tool, char *path, const char *wrap)
 bool is_black_listed_file(const char *name)
 {
     /* used by autoconf */
-    if (STREQ(name, "conftest.c"))
+    if (STREQ(name, "conftest.c") || STREQ(name, "conftest.adb"))
         return true;
 
     /* used by cmake */