https://bugs.webkit.org/show_bug.cgi?id=84229

CMake caches ONLY_BUILD_JAVASCRIPTCORE=1 and will reuse the setting for
subsequent builds, stopping WebCore from being built ever again.

Instead of trying to emulate a build target using command line options,
just build the existing jsc target directly.

Patch by Thiago Marcos P. Santos <thiago.santos@intel.com> on 2012-04-18
Reviewed by Rob Buis.

.:

* CMakeLists.txt:

Tools:

* Scripts/build-jsc:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114508 268f45cc-cd09-0410-ab3c-d52691b4dbfc