[Autotools] Prepend the WebCore layer archives' names with 'lib'

[Autotools] Prepend the WebCore layer archives' names with 'lib'
https://bugs.webkit.org/show_bug.cgi?id=125627

Reviewed by Martin Robinson.

Source/WebKit2:

* GNUmakefile.am: Libtool can complain about the WebCore layer archives not being prepended with 'lib'
when they are used during linking, so the prefix is now added to avoid such issues.

Tools:

* TestWebKitAPI/GNUmakefile.am: Libtool can complain about the WebCore layer archives not being prepended
with 'lib' when they are used during linking, so the prefix is now added to avoid such issues.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@160490 268f45cc-cd09-0410-ab3c-d52691b4dbfc