cli: add support for PKG_CONFIG_MSVC_SYNTAX env variable

Patch from Dan Kegel.

NEWS

@@ -18,6 +18,8 @@ Changes from 1.6.3 to 1.7.0:
   - A new --shared option and WantDefaultStatic cross-compile
     configuration option have been added.  This allows for toolchains
     to specify that static linking should be used by default.
+  - Support for the PKG_CONFIG_MSVC_SYNTAX environment variable has
+    been added.  Patch by Dan Kegel.
 
 Changes from 1.6.2 to 1.6.3:
 ----------------------------

cli/main.c

@@ -971,7 +971,7 @@ main(int argc, char *argv[])
 	pkgconf_client_init(&pkg_client, error_handler, NULL, personality);
 
 #ifndef PKGCONF_LITE
-	if ((want_flags & PKG_MSVC_SYNTAX) == PKG_MSVC_SYNTAX)
+	if ((want_flags & PKG_MSVC_SYNTAX) == PKG_MSVC_SYNTAX || getenv("PKG_CONFIG_MSVC_SYNTAX") != NULL)
 		want_render_ops = msvc_renderer_get();
 #endif
 

man/pkgconf.1

@@ -211,6 +211,8 @@ If set, enables additional debug logging.
 The format of the debug log messages is implementation-specific.
 .It Va PKG_CONFIG_DONT_RELOCATE_PATHS
 If set, disables the path relocation feature.
+.It Va PKG_CONFIG_MSVC_SYNTAX
+If set, uses MSVC syntax for fragments.
 .El
 .Sh EXAMPLES
 Displaying the CFLAGS of a package: