[lldb] Fix lldb build on musl

Summary: limits.h is needed for getting PATH_MAX definition, this comes to fore
with musl libc where limits.h is not included indirectly via other system headers.

Patch by Khem Raj, thanks!

Reviewers: compnerd

Reviewed By: compnerd

Subscribers: llvm-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D31275

llvm-svn: 340876

lldb/source/Utility/FileSpec.cpp

@@ -27,6 +27,7 @@
 #include <vector>       // for vector
 
 #include <assert.h> // for assert
+#include <limits.h> // for PATH_MAX
 #include <stdio.h>  // for size_t, NULL, snpr...
 #include <string.h> // for strcmp