ghc: install static gmp in prefix

Library/Formula/ghc.rb

@@ -73,7 +73,7 @@ def install
     ENV.m32 if build.build_32_bit?
 
     # Build a static gmp (to avoid dynamic linking to ghc)
-    gmp_prefix = buildpath/"gmp-static"
+    gmp_prefix = libexec/"gmp-static"
     resource("gmp").stage do
       gmp_args = ["--prefix=#{gmp_prefix}", "--enable-cxx", "--enable-shared=no"]
       gmp_args << "ABI=32" if build.build_32_bit?
@@ -84,8 +84,7 @@ def install
       system "./configure", *gmp_args
       system "make"
       system "make", "check"
-      ENV.deparallelize
-      system "make", "install"
+      system "make", "-j1", "install"
     end
 
     # Move the main tarball contents into a subdirectory
@@ -134,8 +133,8 @@ def install
       system "./configure", "--prefix=#{prefix}",
                             "--build=#{arch}-apple-darwin",
                             "--with-gcc=#{ENV.cc}",
-                            "--with-gmp-includes=#{gmp_prefix}",
-                            "--with-gmp-libraries=#{gmp_prefix}"
+                            "--with-gmp-includes=#{gmp_prefix}/include",
+                            "--with-gmp-libraries=#{gmp_prefix}/lib"
       system "make"
 
       if build.with? "tests"