nlopt: Explicitly disable plugins

They might find the config scripts for build machine.

Should fix #533.
geos: Fix geos-config script

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
gdal: Update and fix config script locations

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
gdal: Remove remnants of i686-pc-mingw32

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
libxml2: Symlink config script to standard location

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
gdal: Fix library detection

Also add libxml2 support

Signed-off-by: Timothy Gu <timothygu99@gmail.com>
jpeg: Fix jmorecfg.h patch

Fixes compiling graphicsmagick

Signed-off-by: Timothy Gu <timothygu99@gmail.com>