build: Fix mingw ssl gdi32 order

- If mingw ssl make sure -lgdi32 comes after ssl libs

- Allow PKG_CONFIG to set pkg-config location and options

Bug: https://github.com/bagder/curl/pull/501
Reported-by: Kang Lin

acinclude.m4

@@ -3052,9 +3052,17 @@ dnl Optionally PKG_CONFIG_LIBDIR may be given as $pcdir.
 dnl
 
 AC_DEFUN([CURL_CHECK_PKGCONFIG], [
-    AC_PATH_TOOL( PKGCONFIG, pkg-config, no, $PATH:/usr/bin:/usr/local/bin)
 
-    if test x$PKGCONFIG != xno; then
+    if test -z "$PKGCONFIG"; then
+      PKGCONFIG="$PKG_CONFIG"
+    fi
+
+    if test -z "$PKGCONFIG"; then
+      AC_PATH_TOOL([PKGCONFIG], [pkg-config], [no],
+        [$PATH:/usr/bin:/usr/local/bin])
+    fi
+
+    if test "x$PKGCONFIG" != "xno"; then
       AC_MSG_CHECKING([for $1 options with pkg-config])
       dnl ask pkg-config about $1
       itexists=`CURL_EXPORT_PCDIR([$2]) dnl

configure.ac

@@ -1399,6 +1399,24 @@ if test "$curl_ssl_msg" = "$init_ssl_msg" && test X"$OPT_SSL" != Xno; then
   CLEANCPPFLAGS="$CPPFLAGS"
   CLEANLIBS="$LIBS"
 
+  dnl This is for Msys/Mingw
+  case $host in
+    *-*-msys* | *-*-mingw*)
+      AC_MSG_CHECKING([for gdi32])
+      my_ac_save_LIBS=$LIBS
+      LIBS="-lgdi32 $LIBS"
+      AC_TRY_LINK([#include <windef.h>
+                   #include <wingdi.h>],
+                   [GdiFlush();],
+                   [ dnl worked!
+                   AC_MSG_RESULT([yes])],
+                   [ dnl failed, restore LIBS
+                   LIBS=$my_ac_save_LIBS
+                   AC_MSG_RESULT(no)]
+                  )
+      ;;
+  esac
+
   case "$OPT_SSL" in
   yes)
     dnl --with-ssl (without path) used
@@ -1477,24 +1495,6 @@ if test "$curl_ssl_msg" = "$init_ssl_msg" && test X"$OPT_SSL" != Xno; then
   CPPFLAGS="$CPPFLAGS $SSL_CPPFLAGS"
   LDFLAGS="$LDFLAGS $SSL_LDFLAGS"
 
-  dnl This is for Msys/Mingw
-  case $host in
-    *-*-msys* | *-*-mingw*)
-      AC_MSG_CHECKING([for gdi32])
-      my_ac_save_LIBS=$LIBS
-      LIBS="-lgdi32 $LIBS"
-      AC_TRY_LINK([#include <windef.h>
-                   #include <wingdi.h>],
-                   [GdiFlush();],
-                   [ dnl worked!
-                   AC_MSG_RESULT([yes])],
-                   [ dnl failed, restore LIBS
-                   LIBS=$my_ac_save_LIBS
-                   AC_MSG_RESULT(no)]
-                  )
-      ;;
-  esac
-
   AC_CHECK_LIB(crypto, HMAC_Update,[
      HAVECRYPTO="yes"
      LIBS="-lcrypto $LIBS"