libGL: expand the stack size on musl when creating new threads.

fixes #933.

srcpkgs/libGL/patches/musl-stacksize.patch

@@ -0,0 +1,35 @@
+diff --git ./include/c11/threads_posix.h ./include/c11/threads_posix.h
+index 45cb6075e6..1a2ea1a450 100644
+--- ./include/c11/threads_posix.h
++++ ./include/c11/threads_posix.h
+@@ -281,15 +281,29 @@ static inline int
+ thrd_create(thrd_t *thr, thrd_start_t func, void *arg)
+ {
+     struct impl_thrd_param *pack;
++#ifdef __GLIBC__
++    pthread_attr_t *attrp = NULL;
++#else
++    pthread_attr_t attr = { 0 };
++    pthread_attr_init(&attr);
++    pthread_attr_setstacksize(&attr, 8388608);
++    pthread_attr_t *attrp = &attr;
++#endif
+     assert(thr != NULL);
+     pack = (struct impl_thrd_param *)malloc(sizeof(struct impl_thrd_param));
+     if (!pack) return thrd_nomem;
+     pack->func = func;
+     pack->arg = arg;
+-    if (pthread_create(thr, NULL, impl_thrd_routine, pack) != 0) {
++    if (pthread_create(thr, attrp, impl_thrd_routine, pack) != 0) {
++#ifndef __GLIBC__
++        pthread_attr_destroy(&attr);
++#endif
+         free(pack);
+         return thrd_error;
+     }
++#ifndef __GLIBC__
++    pthread_attr_destroy(&attr);
++#endif
+     return thrd_success;
+ }
+ 

srcpkgs/libGL/template

@@ -1,7 +1,7 @@
 # Template file for 'libGL'
 pkgname=libGL
 version=18.1.4
-revision=1
+revision=2
 wrksrc="mesa-${version}"
 build_style=gnu-configure
 configure_args="--enable-shared-glapi --enable-gbm