Use locally provided gc headers.

(cherry picked from commit 198aebba)

component/w3m/buildout.cfg

@@ -42,6 +42,6 @@ patches =
 
 environment =
   PATH=${pkgconfig:location}/bin:%(PATH)s
-  PKG_CONFIG_PATH=${openssl:location}/lib/pkgconfig
-  CPPFLAGS=-I${ncurses:location}/include/ -I${zlib:location}/include/
+  PKG_CONFIG_PATH=${openssl:location}/lib/pkgconfig:${garbage-collector:location}/lib/pkconfig
+  CPPFLAGS=-I${ncurses:location}/include/ -I${zlib:location}/include/ -I${garbage-collector:location}/include
   LDFLAGS=-Wl,--as-needed -L${garbage-collector:location}/lib -Wl,-rpath=${garbage-collector:location}/lib -L${ncurses:location}/lib -Wl,-rpath=${ncurses:location}/lib -L${openssl:location}/lib -Wl,-rpath=${openssl:location}/lib -L${zlib:location}/lib -Wl,-rpath=${zlib:location}/lib