patch 9.1.0104: Linking fails with -lto because of PERL_CFLAGS

Problem:  Linking fails with -lto because of PERL_CFLAGS
          (Zoltan Toth)
Solution: Filter out -flto argument from Perl CFLAGS.

fixes: #14012

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/configure.ac b/src/configure.ac
index ebe0d08..664f219 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -1163,11 +1163,13 @@
       dnl Remove "-fno-something", it breaks using cproto.
       dnl Remove "-fdebug-prefix-map", it isn't supported by clang.
       dnl Remove "FORTIFY_SOURCE", it will be defined twice.
-      dnl remove -pipe and -Wxxx, it confuses cproto
+      dnl Remove -pipe and -Wxxx, it confuses cproto
+      dnl Remove -flto[=auto], it causes link failures for clang
       perlcppflags=`$vi_cv_path_perl -Mlib=$srcdir -MExtUtils::Embed \
 		-e 'ccflags;perl_inc;print"\n"' | sed -e 's/-fno[[^ ]]*//' \
 		-e 's/-fdebug-prefix-map[[^ ]]*//g' \
 		-e 's/-pipe //' \
+		-e 's/-flto\(=auto\)\? //' \
 		-e 's/-W[[^ ]]*//g' \
 		-e 's/-D_FORTIFY_SOURCE=.//g'`
       dnl Remove "-lc", it breaks on FreeBSD when using "-pthread".