fragment: Mingw needs to use POSIX handling for `\\`

Otherwise it won't correctly escape things like spaces, and can print
out the `\` literal escaping nothing, which causes most shell lexers to
choke.

Fixes: #238

Makefile.am

@@ -95,6 +95,7 @@ EXTRA_DIST =	pkg.m4 \
 		tests/lib1/metapackage-2.pc \
 		tests/lib1/explicit-sysroot.pc \
 		tests/lib1/escaped-backslash.pc \
+		tests/lib1/escaped-space.pc \
 		tests/lib1/cflags-internal.pc \
 		tests/lib1/requires-internal.pc \
 		tests/lib1/requires-internal-2.pc \

libpkgconf/fragment.c

@@ -438,7 +438,7 @@ fragment_quote(const pkgconf_fragment_t *frag)
 		    (*src > ':' && *src < '=') ||
 		    (*src > '=' && *src < '@') ||
 		    (*src > 'Z' && *src < '\\') ||
-#ifndef _WIN32
+#if !defined(_WIN32) && !defined(__MINGW32__)
 		    (*src == '\\') ||
 #endif
 		    (*src > '\\' && *src < '^') ||

tests/lib1/escaped-space.pc

@@ -0,0 +1,4 @@
+Name: escaped-space
+Version: 1
+Description: test package for backslash escape of spaces
+Cflags: -IC:\\A\ space

tests/parser.sh

@@ -138,6 +138,14 @@ escaped_backslash_body()
 		pkgconf --with-path=${selfdir}/lib1 --cflags escaped-backslash
 }
 
+escaped_space_body()
+{
+	atf_check \
+		-e ignore \
+		-o inline:"-IC:\\\\\\\\A space\n" \
+		pkgconf --with-path=${selfdir}/lib1 --cflags escaped-space
+}
+
 quoted_body()
 {
 	export PKG_CONFIG_PATH="${selfdir}/lib1"