It is better to use environment variables (GOOS and GOARCH) for
consistency instead of providing two slightly incompatible ways. This
-target flag should only be used to specify a .json file (either
directly or in the TinyGo targets directory). Previously it was possible
to specify the LLVM target as well but that was never really fully
supported.
So:
- To specify a different OS/arch like you would in regular Go, use
GOOS and GOARCH.
- To specify a microcontroller chip or board, use the -target flag.
Also remove the old `os.Setenv` which might have had a purpose long ago
but doesn't have a purpose now.
... instead of setting a special -target= value. This is more robust and
makes sure that the test actually tests different arcitectures as they
would be compiled by TinyGo. As an example, the bug of the bugfix in the
previous commit ("arm: use armv7 instead of thumbv7") would have been
caught if this change was applied earlier.
I've decided to put GOOS/GOARCH in compileopts.Options, as it makes
sense to me to treat them the same way as command line parameters.
