Allow custom build directory

[stefanv]

Closes #171

• Add -C flag to meson commands
• Add tests and verify that compilation happens in right place

[stefanv]

@lagru Ready for testing.

[lagru]

Thanks @stefanv! I played around with it locally and came up with a few limitations. Would be good to iterate further on the API and behavior. :)

[lagru]

The name build-clang might be a bit misleading. To me it implies that this feature can somehow be used to choose a different compiler (clang). As I understand it, you'd need to update the underlying "build" command / configuration which would then apply regardless of build directory? Or am I missing something?

[lagru]

spin -C ${SOME_DIR} command seems to fail. I think this is because the option is added ad subcommand level. So this alias won't work currently. I think the option would need to be added to the top-level spin command and then passed down via the context.

[stefanv]

Right, may have to rethink that. We don't have global context in spin.

[stefanv]

@lagru Please take another look; the build directory can now be absolute, and can be set using SPIN_BUILD_DIR, which is helpful for creating an alias. I also updated the alias to be a better example, showing how to set the compiler to clang and build into a different build directory using clang.

[lagru]

Thanks. Absolute, relative and nested-relative paths seem to work perfectly now. I'm not familiar with the code base so take my approval with a grain of salt. ;)

[oscarbenjamin]

Nice!

I was just about to suggest this feature. I just gave it a quick er... spin and it seems to work exactly as I wanted.

One suggestion though:

When you run meson setup build-dir it adds a .gitignore to the build directory. I already have a .gitignore entry for the build-install directory but if I do:

meson setup build-release -Dbuildtype=release
spin -C build-release run ...

Then the build-release-install directory is created but it does not have any .gitignore file. Perhaps spin could create the directory and add the .gitignore file before running meson install.

[stefanv]

@oscarbenjamin What you request sounds very reasonable, but it's already the way my setup behaves:

$ spin build -C build-xyz && ls -al build-xyz/.gitignore
-rw-r--r--. 1 stefan stefan 92 Sep  2 21:05 build-xyz/.gitignore

I see the same behavior when adding the -Dbuildtype=release flag.

[oscarbenjamin]

it's already the way my setup behaves:

I've just checked again and confirm that the .gitignore is not added here:

$ spin build -C build-foo -- --pkg-config-path=.local/lib/pkgconfig -Dadd_flint_rpath=true
...
$ git status
On branch pr_nmod_ctx
Your branch is up-to-date with 'origin/pr_nmod_ctx'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)
	build-abc-install/
	build-foo-install/
	build-xyz-install/

nothing added to commit but untracked files present (use "git add" to track)

Is it meson that adds it in the meson install step?

I didn't expect that meson install would do that so it didn't seem surprising that the .gitignore was not being added.