Generate a libgtest.la to help libtool managing dependencies

When building and using googletest from an install tree
we want libtool to generate rpath in the dependent binaries
to allow them to be executed from a build without a need
for LD_LIBRARY_PATH or similar.

For libtool based project this happens automatically
as projects generates .la files and install them.
Provide such a file for gtest as well to allow it to
work smoothly with libtool based projects.
Signed-off-by: Knut Omang <knut.omang@oracle.com>

googletest/cmake/libgtest.la.in

+# libgtest.la - a libtool library file
+# Generated by libtool (GNU libtool) 2.4.6
+
+# Please DO NOT delete this file!
+# It is necessary for linking the library.
+
+# Names of this library.
+library_names='libgtest.so'
+
+# Is this an already installed library?
+installed=yes
+
+# Should we warn about portability when linking against -modules?
+shouldnotlink=no
+
+# Files to dlopen/dlpreopen
+dlopen=''
+dlpreopen=''
+
+# Directory that this library needs to be installed in:
+libdir='@CMAKE_INSTALL_FULL_LIBDIR@'