This commit also adds a bit of version independence, in particular for
external commands. It also adds the LLVM version to the `tinygo version`
command, which might help while debugging.
This hack was originally introduced in
https://github.com/tinygo-org/tinygo/pull/251 to fix an escape analysis
regression after https://github.com/tinygo-org/tinygo/pull/222
introduced nil checks. Since a new optimization in LLVM (see
https://reviews.llvm.org/D60047) this hack is not necessary anymore and
can be removed.
I've compared all regular tests and smoke tests before and after to
check the size. In most cases this change was an improvement although
there are a few regressions.
This commit makes a number of changes:
* It avoids a dependency on Compiler.emitStartGoroutine.
* It moves the func-lowering pass to the transform package.
* It adds testing to func lowering.
No functionality should have changed with this commit.
