mk: Split target triples into bulid triple + host triples + target tr…
For cross compiling to targets that don't want to build a compiler
build: Stop passing --lib argument
Adjust perf target to use correct variable names
build: Fix 'make perf'. Closes #1151
Run perf on the stage 2 compiler
Abstract the build directories further in the makefiles
This defines variables for host bin and lib directories as well as all target
bin and lib directories then uses them everywhere.
Fix a variety of things in the makefiles
Make tests and perf work again. Correctly get the host triple in rustc. Add
some FIXMEs about transitional code that needs to be removed.