[lldb] Fix lldb build on musl

[raj.khem]

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.

[tatyana-krasnukha]

Looks reasonable, limits.h really is not included by any of these system headers in musl.

[raj.khem]

Can someone with commit access push this for me please ?

source/Utility/FileSpec.cpp

 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
 
 #include <algorithm>    // for replace, min, unique
 #include <system_error> // for error_code
 #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
 
 using namespace lldb;
 using namespace lldb_private;
 
 namespace {