[CMake] Always build wtf as a static library.

[CMake] Always build wtf as a static library.
https://bugs.webkit.org/show_bug.cgi?id=79857

Reviewed by Eric Seidel.

.:

* CMakeLists.txt: Put static libraries in ${CMAKE_BINARY_DIR} too
to have them grouped with the shared ones.

Source/JavaScriptCore:

To help the efforts in bug 75673 to move WTF out of
JavaScriptCore, act more like the other ports and remove the
possibility of building WTF as a shared library.

It does not make much sense to, for example, ship WTF as a
separate .so with webkit-efl packages, and it should be small
enough not to cause problems during linking.

* wtf/CMakeLists.txt:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@109197 268f45cc-cd09-0410-ab3c-d52691b4dbfc