Do not strcat to result of getenv.

	PR lto/94157
	* lto-wrapper.c (run_gcc): Use concat for appending
	to collect_gcc_options.
	PR lto/94157
	* gcc.dg/lto/pr94157_0.c: New test.

gcc/ChangeLog

+2020-03-13  Martin Liska  <mliska@suse.cz>
+
+	PR lto/94157
+	* lto-wrapper.c (run_gcc): Use concat for appending
+	to collect_gcc_options.
+
 2020-03-13  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/94121

gcc/lto-wrapper.c

@@ -1317,7 +1317,8 @@ run_gcc (unsigned argc, char *argv[])
 
       char *xassembler_opts_string
 	= XOBFINISH (&temporary_obstack, char *);
-      strcat (collect_gcc_options, xassembler_opts_string);
+      collect_gcc_options = concat (collect_gcc_options, xassembler_opts_string,
+				    NULL);
     }
 
   get_options_from_collect_gcc_options (collect_gcc, collect_gcc_options,

gcc/testsuite/ChangeLog

+2020-03-13  Martin Liska  <mliska@suse.cz>
+
+	PR lto/94157
+	* gcc.dg/lto/pr94157_0.c: New test.
+
 2020-03-13  Kewen Lin  <linkw@gcc.gnu.org>
 
 	PR testsuite/93935

gcc/testsuite/gcc.dg/lto/pr94157_0.c

+/* { dg-lto-do link } */
+/* { dg-lto-options { { -O0 -fipa-vrp -flto -Wa,--noexecstack -Wa,--noexecstack -Wa,--execstack  -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack -Wa,--execstack } } } */
+
+int main() {
+
+}