thunderbird: Pick libGL.so for NetBSD in GLContextProviderGLX.cpp

NetBSD ships with libGL.so.3 as of NetBSD-8.99.42 and the libGL.so form
is more portable.

mail/thunderbird/distinfo

@@ -1,4 +1,4 @@
-$NetBSD: distinfo,v 1.209 2019/05/27 13:06:18 ryoon Exp $
+$NetBSD: distinfo,v 1.210 2019/06/01 23:27:58 kamil Exp $
 
 SHA1 (thunderbird-60.7.0.source.tar.xz) = 23b4227d9459d2100f580af68139f6641fc24c66
 RMD160 (thunderbird-60.7.0.source.tar.xz) = 715048ca1b84353442321098e4d63aa4079ef24e
@@ -16,6 +16,7 @@ SHA1 (patch-comm_mail_installer_package-manifest.in) = 14e8977f690e579a8caf73326
 SHA1 (patch-comm_mail_installer_removed-files.in) = bda8a8d12075fa5bf87d552035812f5cf485a393
 SHA1 (patch-dom_media_CubebUtils.cpp) = 76fc35167e603f96450f4bc17cd0d76157a22dd3
 SHA1 (patch-gfx_angle_checkout_src_common_third__party_smhasher_src_PMurHash.cpp) = 23c0f9d4677c1a87ebeb12a9a822fd7a15f51215
+SHA1 (patch-gfx_gl_GLContextProviderGLX.cpp) = 4b85e9bf5a199b450c56790d5f14e6bdc7867c33
 SHA1 (patch-gfx_webrender_src_query.rs) = 3e5fe60706a4b6daf14861aedf37ac86a8acad18
 SHA1 (patch-ipc_chromium_src_base_lock__impl__posix.cc) = a03d220132f86eed32117a1d0282064a8eff46ca
 SHA1 (patch-ipc_chromium_src_base_message__pump__libevent.cc) = cdb159f0ede970b150eca4cc5e0d1b2cf4e414b2

mail/thunderbird/patches/patch-gfx_gl_GLContextProviderGLX.cpp

@@ -0,0 +1,15 @@
+$NetBSD: patch-gfx_gl_GLContextProviderGLX.cpp,v 1.1 2019/06/01 23:27:58 kamil Exp $
+
+Pick portable version of libGL.so.
+
+--- gfx/gl/GLContextProviderGLX.cpp.orig	2019-05-17 12:04:28.000000000 +0000
++++ gfx/gl/GLContextProviderGLX.cpp
+@@ -80,7 +80,7 @@ bool GLXLibrary::EnsureInitialized() {
+     // implementation requires an executable stack, which causes mprotect calls,
+     // which trigger glibc bug
+     // http://sourceware.org/bugzilla/show_bug.cgi?id=12225
+-#ifdef __OpenBSD__
++#if defined(__OpenBSD__) || defined(__NetBSD__)
+     libGLfilename = "libGL.so";
+ #else
+     libGLfilename = "libGL.so.1";