compat.glfw: declare abi:glibc capability (linux) (#33)

Lets mcpp enforce that GLFW consumers use a glibc toolchain (it links the
glibc X11/GL world); musl-static now fails fast with an actionable ABI error
instead of a cryptic arc4random_buf failure.

Co-authored-by: sunrisepeak <x.d2learn.org@gmail.com>

Author: Sunrisepeak

pkgs/c/compat.glfw.lua

@@ -56,7 +56,7 @@ package = {
             cflags = { "-D_DEFAULT_SOURCE", "-D_GLFW_X11" },
             runtime = {
                 dlopen_libs = { "libGLX.so.0", "libGL.so.1", "libGL.so" },
-                capabilities = { "x11.display", "opengl.glx.driver" },
+                capabilities = { "x11.display", "opengl.glx.driver", "abi:glibc" },
             },
             sources = {
                 "src/x11_init.c",