patch libffi.pc.in file

patch/ffi.patch

@@ -0,0 +1,15 @@
+--- a/libffi.pc.in
++++ b/libffi.pc.in
+@@ -1,4 +1,4 @@
+-prefix=@prefix@
++prefix=
+ exec_prefix=@exec_prefix@
+ libdir=@libdir@
+ toolexeclibdir=@toolexeclibdir@
+@@ -7,5 +7,5 @@
+ Name: @PACKAGE_NAME@
+ Description: Library supporting Foreign Function Interfaces
+ Version: @PACKAGE_VERSION@
+-Libs: -L${toolexeclibdir} -lffi
++Libs: ${toolexeclibdir}/libffi.a
+ Cflags: -I${includedir}