gdb: add patches from sabotage to make this build/work with musl.

srcpkgs/gdb/patches/gdb-linux_nat.patch

@@ -0,0 +1,30 @@
+the first chunk fixes build errors,
+the non_stop part below fixes thread debugging being available
+by default without setting any breakpoints or usage of libthread_db.
+
+--- gdb-7.4.org/gdb/linux-nat.c	2013-08-10 05:24:24.651000003 +0000
++++ gdb-7.4/gdb/linux-nat.c	2013-08-10 05:25:50.966000003 +0000
+@@ -71,6 +71,14 @@
+ # endif
+ #endif /* HAVE_PERSONALITY */
+ 
++#ifndef __SIGRTMIN
++#define __SIGRTMIN SIGRTMIN
++#endif
++
++#ifndef W_STOPCODE
++#define W_STOPCODE(sig) ((sig) << 8 | 0x7f)
++#endif
++
+ /* This comment documents high-level logic of this file.
+ 
+ Waiting for events in sync mode
+@@ -2265,7 +2273,7 @@
+ 		status = 0;
+ 	    }
+ 
+-	  if (non_stop)
++	  if (1)
+ 	    {
+ 	      /* Add the new thread to GDB's lists as soon as possible
+ 		 so that: