osxfuse_requirement: add library and include paths

In the installation whose prefix is other than /usr/local,
osxfuse library and include path must explicitly be specified during build.
Although brew's pkg-config is configured to prepend appropriates paths,
the prepended paths (/usr/local) supercede the original HOMEBREW_PREFIX.
This behavior will cause the linker to select libraries outside brew's tree.

By adding /usr/local to HOMEBREW_LIBRARY_PATHS, superenv ensures that appears
only after the HOMEBREW_PREFIX, and thus fixes this problem.

HOMEBREW_INCLUDE_PATHS is also configured like keg-only Formulae.

Library/Homebrew/requirements/osxfuse_requirement.rb

@@ -14,6 +14,11 @@ class OsxfuseRequirement < Requirement
 
   env do
     ENV.append_path "PKG_CONFIG_PATH", HOMEBREW_LIBRARY/"Homebrew/os/mac/pkgconfig/fuse"
+
+    unless HOMEBREW_PREFIX.to_s == "/usr/local"
+      ENV.append_path "HOMEBREW_LIBRARY_PATHS", "/usr/local/lib"
+      ENV.append_path "HOMEBREW_INCLUDE_PATHS", "/usr/local/include/osxfuse"
+    end
   end
 end