try_compile: Fix quoting of libraries in generated CMakeLists.txt

Since commit 236133e7 (Handle targets in the LINK_LIBRARIES of
try_compile, 2013-02-09) libraries passed to the new LINK_LIBRARIES
option of try_compile are not quoted inside the generated CMakeLists.txt
file.  Quote the library names so they re-parse correctly when loaded by
CMake to configure and generate the test project.

Reported-by: Bogdan Cristea <cristeab@gmail.com>
Merge topic 'fix-try_compile-library-spaces' into next

e65ef08 try_compile: Fix quoting of libraries in generated CMakeLists.txt