libc: core: print error message on assertion failure

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "lib/libfx"]
 	path = lib/libfx
 	url = https://g.wash.red/wash/fx.git
+[submodule "programs/bshell"]
+	path = programs/bshell
+	url = https://g.wash.red/wash/bshell.git

lib/libc/core/assert/assert.c

@@ -1,3 +1,5 @@
+#include <magenta/log.h>
+#include <stdio.h>
 #include <stdlib.h>
 
 extern void __libc_assert_failed(
@@ -6,5 +8,6 @@ extern void __libc_assert_failed(
 	const char *func,
 	const char *cond)
 {
+	kern_logf("ASSERT: %s failed (%s in %s:%d)", cond, func, file, line);
 	abort();
 }