This flag is overloaded. It can be used in two ways:
* Choosing the flash method to use (openocd, msd, command).
* Choosing the OpenOCD programmer name.
For example, you can use one of these to use OpenOCD instead of the
mass-storage device programmer:
tinygo flash -target=microbit -programmer=openocd
tinygo flash -target=microbit -programmer=cmsis-dap
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.
Setting the linker script as one property (instead of as part of the
generic ldflags property) allows it to be overriden.
This is important for the SoftDevice on Nordic chips, because the
SoftDevice takes up a fixed part of the flash/RAM and the application
must be flashed at a different position. With this linkerscript option,
it is possible to create (for example) a pca10040-s132v6 that overrides
the default linker script.
Move most of the logic of determining which compiler configuration to
use (such as GOOS/GOARCH, build tags, whether to include debug symbols,
panic strategy, etc.) into the compileopts package. This makes it a
single source of truth for anything related to compiler configuration.
It has a few advantages:
* The compile configuration is independent of the compiler package.
This makes it possible to move optimization passes out of the
compiler, as they don't rely on compiler.Config anymore.
* There is only one place to look if an incorrect compile option is
used.
* The compileopts provides some resistance against unintentionally
picking the wrong option, such as with c.selectGC() vs c.GC() in the
compiler.
* It is now a lot easier to change compile options, as most options
are getters now.
