Fix pkgconfig file's entries

cppad-fix_pkgconfig.patch

@@ -0,0 +1,26 @@
+--- a/pkgconfig/cppad.pc.orig.in	2021-02-18 14:28:40.000000000 +0100
++++ b/pkgconfig/cppad.pc.in	2021-07-28 18:23:38.761860174 +0200
+@@ -15,9 +15,9 @@
+ # for the meaning of these variables.
+ #
+ prefix=@cppad_prefix@
+-exec_prefix=$(prefix)
+-includedir=${prefix}/@cppad_includedir@
+-libdir=${exec_prefix}/@cppad_libdir@
++exec_prefix=@cppad_prefix@
++includedir=@cppad_prefix@/${cmake_install_includedirs}/cppad
++libdir=@cppad_prefix@/${cmake_install_libdirs}
+ #
+ # See https://people.freedesktop.org/~dbn/pkg-config-guide.html
+ # for the meaning of the settings below:
+@@ -27,8 +27,8 @@
+ Version:               @cppad_version@
+ URL:                   @cppad_url@
+ #
+-Cflags:                -I${includedir}
+-Libs:                  -L{libdir} -l@cppad_lib_list@
++Cflags:                -I@cppad_prefix@/${cmake_install_includedirs}/cppad
++Libs:                  -L@cppad_prefix@/${cmake_install_libdirs} @cppad_lib_list@
+ Requires:
+ Libs.private           @cppad_libs_private@
+ Requires.private:      @cppad_requires_private@