Use LLDB_SRC for relative paths
Use LLDB_SRC for relative paths

Summary:
Going from LLDB_SRC instead of the file path is safer when looking for compiler-rt. Also need to add support for looking inside the LLVM runtimes subdirectory.

Eventually we should just get CMake to provide these paths during configuration.

Reviewers: tfiala, zturner

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D25489

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@284045 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb