[gimp] configure.ac: escape backslash chars in compiler version string

[Ell <ell src gnome org>]

commit c0b107531e65e47149c248449ca7bac8d20632ee
Author: Ell <ell_se yahoo com>
Date:   Sun Nov 11 05:45:07 2018 -0500

    configure.ac: escape backslash chars in compiler version string
    
    When constructing CC_VERSION, escape backslash characters in the
    compiler version string, so that they don't get interpreted as
    escape sequences by the compiler.  This is especially important on
    Windows, where the version string of MinGW may contain backslash
    characters as part of paths.

 configure.ac | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7bfccdc972..5474e774f2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -580,21 +580,23 @@ WARNING: GCC 7.2.0 has a serious bug affecting GEGL/GIMP. We advise
          See https://bugzilla.gnome.org/show_bug.cgi?id=787222";
   fi
   # For GCC, use -v which has more information than --version.
-  CC_VERSION="\\\\t`$CC -v 2>&1 | sed -e 's/$/\\\\n\\\\t/g' | tr -d '\n'`"
+  CC_VERSION="`$CC -v 2>&1`"
 else
   # This is the list of common options used by autotools to check
   # versions for various compilers.
-  CC_VERSION="\\\\t`$CC --version 2>&1 | sed -e 's/$/\\\\n\\\\t/g' | tr -d '\n'`"
+  CC_VERSION="`$CC --version 2>&1`"
   if test $? != 0; then
-    CC_VERSION="\\\\t`$CC -v 2>&1` | sed -e 's/$/\\\\n\\\\t/g' | tr -d '\n'"
+    CC_VERSION="`$CC -v 2>&1`"
     if test $? != 0; then
-      CC_VERSION="\\\\t`$CC -V 2>&1` | sed -e 's/$/\\\\n\\\\t/g' | tr -d '\n'"
+      CC_VERSION="`$CC -V 2>&1`"
       if test $? != 0; then
-        CC_VERSION="\\\\t`$CC -qversion 2>&1` | sed -e 's/$/\\\\n\\\\t/g' | tr -d '\n'"
+        CC_VERSION="`$CC -qversion 2>&1`"
       fi
     fi
   fi
 fi
+# Format and escape CC_VERSION
+CC_VERSION="\\t`echo "$CC_VERSION" | sed -e 's/\\\\/\\\\\\\\/g;s/$/\\\\n\\\\t/g' | tr -d '\n'`"
 AC_SUBST(CC_VERSION)
 
 AC_HEADER_STDC