The cxx_compiler function should not blindly return clang++ as the C++ compiler if $(CC) contains "clang". Instead, it should perform a textual replacement of $(CC) from "clang" to "clang++".  The same is true for "llvm-gcc" to "llvm-g++" and for "gcc" to "g++".  This way, we keep the path component of the $(CC) passed in from the user and do not end up with a mixed toolchains with different paths.
The cxx_compiler function should not blindly return clang++ as the C++ compiler if $(CC) contains "clang".
Instead, it should perform a textual replacement of $(CC) from "clang" to "clang++".  The same is true
for "llvm-gcc" to "llvm-g++" and for "gcc" to "g++".  This way, we keep the path component of the $(CC)
passed in from the user and do not end up with a mixed toolchains with different paths.

Ditto for a newly added function called cxx_linker.


git-svn-id: b33bab8abb5b18c12ee100cd7761ab452d00b2b0@123451 91177308-0d34-0410-b5e6-96231b3b80d8

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