graphicsmagick: Do not install bundled libtool.

- Conflicts with `brew install libtool`.
- Added maintainer-note that this will be fixed in next version.

Closes Homebrew/homebrew#16570.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/graphicsmagick.rb

@@ -27,6 +27,7 @@ class Graphicsmagick < Formula
   option 'with-x', 'Compile with X11 support.'
   option 'without-magick-plus-plus', "Don't build C++ library."
 
+  depends_on 'libtool' => :build
   depends_on 'jpeg' => :recommended
   depends_on :libpng
   depends_on :x11 if build.include? 'with-x'
@@ -48,12 +49,19 @@ class Graphicsmagick < Formula
   def install
     # versioned stuff in main tree is pointless for us
     inreplace 'configure', '${PACKAGE_NAME}-${PACKAGE_VERSION}', '${PACKAGE_NAME}'
+    # Homebrew cleans ".la" files from lib but this configure looks for them.
+    # Maintainers: This will be fixed in the next version >= 1.3.18 (probably)
+    # Then the next line will not be needed anymore. Further the --with-ltdl... flags
+    # further down can be removed then!
+    inreplace 'configure', 'if test -f "$with_ltdl_lib/libltdl.la"', 'if test -f "$with_ltdl_lib/libltdl.a"'
 
     args = ["--disable-dependency-tracking",
             "--prefix=#{prefix}",
             "--enable-shared", "--disable-static"]
     args << "--without-magick-plus-plus" if build.include? 'without-magick-plus-plus'
     args << "--disable-openmp" if MacOS.version == :leopard or not ENV.compiler == :gcc # libgomp unavailable
+    args << "--with-ltdl-include=#{Formula.factory('libtool').opt_prefix}/include"  # avoid to ship it's own ltdl
+    args << "--with-ltdl-lib=#{Formula.factory('libtool').opt_prefix}/lib"  # avoid to ship it's own ltdl
     args << "--with-gslib" if ghostscript_srsly?
     args << "--with-gs-font-dir=#{HOMEBREW_PREFIX}/share/ghostscript/fonts" \
               unless ghostscript_fonts?