Parametrize build via environment variables
Parametrize build via environment variables

build.rs now recognizes next environment variables:
IMAGE_MAGICK_DIR - installation directory
IMAGE_MAGICK_LIB_DIRS - list of lib dirs split by ":"
IMAGE_MAGICK_INCLUDE_DIRS - list of include dirs split by ":"
IMAGE_MAGICK_LIBS - list of the libs to link to
IMAGE_MAGICK_STATIC - if set to value other than 0, link statically

nlfiedler/magick-rust