Curate Mesa's dependencies on X11

[certik]

On my laptop (or any other default Ubuntu installation), Mesa currently depends on some X11 libraries, see below. I don't know if it is possible to get rid of these dependencies or include them in hpcmp2. It's kind of sad, because otherwise the whole VTK works excellent, with only dependencies that we include.

[mesa] checking for pkg-config... /usr/bin/pkg-config
[mesa] checking pkg-config is at least version 0.9.0... yes
[mesa] checking whether gcc supports -Werror=missing-prototypes... yes
[mesa] checking whether gcc supports -fvisibility=hidden... yes
[mesa] checking whether g++ supports -fvisibility=hidden... yes
[mesa] checking whether to enable assembly... yes, x86_64
[mesa] checking for dlopen... no
[mesa] checking for dlopen in -ldl... yes
[mesa] checking for clock_gettime... no
[mesa] checking for clock_gettime in -lrt... yes
[mesa] checking for posix_memalign... yes
[mesa] checking for the pthreads library -lpthreads... no
[mesa] checking whether pthreads work without any flags... no
[mesa] checking whether pthreads work with -Kthread... no
[mesa] checking whether pthreads work with -kthread... no
[mesa] checking for the pthreads library -llthread... no
[mesa] checking whether pthreads work with -pthread... yes
[mesa] checking for joinable pthread attribute... PTHREAD_CREATE_JOINABLE
[mesa] checking if more special flags are required for pthreads... no
[mesa] checking for PTHREAD_PRIO_INHERIT... no
[mesa] configure: Shared GLAPI is only useful for DRI, disabling
[mesa] checking for LIBDRM... no
[mesa] checking for XLIBGL... no
[mesa] configure: error: Package requirements (x11 xext) were not met:
[mesa] 
[mesa] No package 'x11' found
[mesa] No package 'xext' found
[mesa] 
[mesa] Consider adjusting the PKG_CONFIG_PATH environment variable if you
[mesa] installed software in a non-standard prefix.
[mesa] 
[mesa] Alternatively, you may set the environment variables XLIBGL_CFLAGS
[mesa] and XLIBGL_LIBS to avoid the need to call pkg-config.
[mesa] See the pkg-config man page for more details.
[mesa ERROR] Command '['bash', '../bash_script']' returned non-zero exit status 1
[mesa ERROR] command failed (code=1); raising

[certik]

To fix it temporarily, the following packages need to be installed in Ubuntu: libx11-dev, libxext-dev.