Fix FFTS CMake .pc file

diff --git a/lib/ffts/ffts.pc.cmake.in b/lib/ffts/ffts.pc.cmake.in
index 2434abd..43f38e9 100644
--- a/lib/ffts/ffts.pc.cmake.in
+++ b/lib/ffts/ffts.pc.cmake.in
@@ -1,10 +1,10 @@
-prefix=${prefix}
+prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${exec_prefix}
 libdir=${libdir}
 includedir=${includedir}
 
-Name: FFTS
+Name: @CMAKE_PROJECT_NAME@
 Description: fast Fourier transform library
-Version: ${FFTS_VERSION}
+Version: @FFTS_VERSION@
 Libs: -L${libdir} -lffts -lm
 Cflags: -I${includedir}/ffts