This is a large commit that moves all code directly related to
compiling/linking into a new builder package. This has a number of
advantages:
* It cleanly separates the API between the command line and the full
compilation (with a very small API surface).
* When the compiler finally compiles one package at a time (instead of
everything at once as it does now), something will have to invoke it
once per package. This builder package will be the natural place to
do that, and also be the place where the whole process can be
parallelized.
* It allows the TinyGo compiler to be used as a package. A client can
simply import the builder package and compile code using it.
As part of this refactor, the following additional things changed:
* Exported symbols have been made unexported when they weren't needed.
* The compilation target has been moved into the compileopts.Options
struct. This is done because the target really is just another
compiler option, and the API is simplified by moving it in there.
* The moveFile function has been duplicated. It does not really belong
in the builder API but is used both by the builder and the command
line. Moving it into a separate package didn't seem useful either
for what is essentially an utility function.
* Some doc strings have been improved.
Some future changes/refactors I'd like to make after this commit:
* Clean up the API between the builder and the compiler package.
* Perhaps move the test files (in testdata/) into the builder package.
* Perhaps move the loader package into the builder package.
This makes it possible to query these environment variables from
anywhere, which might be useful. More importantly, it puts them in a
central location from where they can be queried, useful for a `go env`
subcommand.
In particular, while LLVM lld supports -L for linker scripts imported
with the `INCLUDE` command, GNU ld does not seem to support this.
This is a prerequisite for supporting the HiFive1 board in the TinyGo
Playground.
On Debian, all LLVM commands have a version suffix (clang-8, ld.lld-8,
wasm-ld-8, etc.). However. Most other distributions only provide a
version prefix for Clang and not for all the other commands.
This commit fixes the issue by trying the command with the version
suffix first and falling back to one without if needed.
This commit adds the TinyGo root directory (`TINYGOROOT`) to the linker
script `-L` search path, so that linker scripts can be found when
running `tinygo` outside of the TinyGo root.
This was already working before when using an external linker by setting
the working directory, but this is not possible when using the internal
linker. However, by adding the root directory to the linker search path
(`-L`), it can now find these linker scripts.
fixes#265
When building statically against LLVM, LLD is also included now. When
included, the built in wasm-ld will automatically be used instead of the
external command.
There is also support for linking ELF files but because lld does not
fully support armv6m this is not yet enabled (it produces a warning).
