Revert "Use pcfiledir for prefix in pkgconfig file"

The change makes implicit assumptions on the layout of the install
tree, which is going to break in many ways.

The correct solution is to use the `PKG_CONFIG_SYSROOT_DIR` variable
to inject the cross-compiled sysroot into `-I` and `-L` paths.

googlemock/cmake/gmock.pc.in

-prefix=${pcfiledir}/../..
-libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
 
 Name: gmock
 Description: GoogleMock (without main() function)

googlemock/cmake/gmock_main.pc.in

-prefix=${pcfiledir}/../..
-libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
 
 Name: gmock_main
 Description: GoogleMock (with main() function)

googletest/cmake/gtest.pc.in

-prefix=${pcfiledir}/../..
-libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
 
 Name: gtest
 Description: GoogleTest (without main() function)

googletest/cmake/gtest_main.pc.in

-prefix=${pcfiledir}/../..
-libdir=${prefix}/@CMAKE_INSTALL_LIBDIR@
-includedir=${prefix}/@CMAKE_INSTALL_INCLUDEDIR@
+libdir=@CMAKE_INSTALL_FULL_LIBDIR@
+includedir=@CMAKE_INSTALL_FULL_INCLUDEDIR@
 
 Name: gtest_main
 Description: GoogleTest (with main() function)