Unreviewed build fix.

* WebKit.vcproj/WebKitExports.def.in:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141958 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Building with MinGW compiler dies with gtest errors
https://bugs.webkit.org/show_bug.cgi?id=108470

Patch by Paweł Forysiuk <tuxator@o2.pl> on 2013-02-05
Reviewed by Martin Robinson.

Variable Libraries_libgtest_la_CXXFLAGS blindly assumes that
pthreads will always be enabled. Make using pthreads for gtest
conditional on the build target.

* gtest/GNUmakefile.am: Set Libraries_libgtest_la_CXXFLAGS accordingly to the build target.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141959 268f45cc-cd09-0410-ab3c-d52691b4dbfc