Use pkg-config on Windows

I've put a pkg-config.exe in the PATH, put a suitable zlib.pc in %DEPS%\lib\pkgconfig, and added that to PKG_CONFIG_PATH.

Then I've applied the following patch to php-src:

 ext/zlib/config.w32      |  6 +++---
 win32/build/confutils.js | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/ext/zlib/config.w32 b/ext/zlib/config.w32
index 3bc24d88e1..623d752e57 100644
--- a/ext/zlib/config.w32
+++ b/ext/zlib/config.w32
@@ -3,9 +3,9 @@
 ARG_ENABLE("zlib", "ZLIB support", "yes");
 
 if (PHP_ZLIB == "yes") {
-	if (CHECK_LIB("zlib_a.lib;zlib.lib", "zlib", PHP_ZLIB) &&
-		CHECK_HEADER_ADD_INCLUDE("zlib.h", "CFLAGS", "..\\zlib;" + php_usual_include_suspects)) {
-
+	if (PKG_CHECK_MODULES("ZLIB", "zlib >= 1.2.11")) {
+		PHP_EVAL_INCLINE(ZLIB_CFLAGS);
+		PHP_EVAL_LIBLINE(ZLIB_LIBS, "zlib");
 		EXTENSION("zlib", "zlib.c zlib_fopen_wrapper.c zlib_filter.c", PHP_ZLIB_SHARED, "/D ZLIB_EXPORTS /DZEND_ENABLE_STATIC_TSRMLS_CACHE=1");
 		AC_DEFINE("HAVE_ZLIB", 1, "Define to 1 if the PHP extension 'zlib' is available.");
 
diff --git a/win32/build/confutils.js b/win32/build/confutils.js
index 3623dcf7e2..63bd1b867a 100644
--- a/win32/build/confutils.js
+++ b/win32/build/confutils.js
@@ -1054,6 +1054,51 @@ function CHECK_HEADER_ADD_INCLUDE(header_name, flag_name, path_to_check, use_env
 	return p;
 }
 
+function PKG_CHECK_MODULES(prefix, list_of_modules)
+{
+	var out;
+	STDOUT.Write("checking for " + list_of_modules + "... ");
+	if (!(out = execute("pkg-config --cflags " + list_of_modules))) {
+		STDOUT.WriteLine("no");
+		return false;
+	}
+	eval(prefix + "_CFLAGS = out");
+	if (!(out = execute("pkg-config --libs " + list_of_modules))) {
+		STDOUT.WriteLine("no");
+		return false;
+	}
+	eval(prefix + "_LIBS = out");
+	STDOUT.WriteLine("yes");
+	return true;
+}
+
+function PHP_EVAL_LIBLINE(libline, libs_variable, not_extension)
+{
+	libs_variable = libs_variable.toUpperCase();
+	var args = libline.split(/\s/);
+	for (var i = 0; i < args.length; i++) {
+		var arg = args[i];
+		if (arg.match(/^-l(.*)/)) {
+			ADD_FLAG("LIBS_" + libs_variable, RegExp.$1 + ".lib");
+		} else if (arg.match(/^-L(.*)/)) {
+			var path = condense_path(RegExp.$1);
+			ADD_FLAG("LDFLAGS_" + libs_variable, '/libpath:"' + path + '" ');
+			ADD_FLAG("ARFLAGS_" + libs_variable, '/libpath:"' + path + '" ');
+		}
+	}
+}
+
+function PHP_EVAL_INCLINE(headerline)
+{
+	var args = headerline.split(/\s/);
+	for (var i = 0; i < args.length; i++) {
+		var arg = args[i];
+		if (arg.match(/^-I(.*)/)) {
+			ADD_FLAG("CFLAGS", "/I " + condense_path(RegExp.$1));
+		}
+	}
+}
+
 /* XXX check whether some manifest was originally supplied, otherwise keep using the default. */
 function generate_version_info_manifest(makefiletarget)
 {