rustbuild: Use src/rustc for assembled compilers

[alexcrichton]

The src/rustc path is intended for assembling a compiler (e.g. the bare bones)
not actually compiling the whole compiler itself. This path was accidentally
getting hijacked to represent the whole compiler being compiled, so let's
redirect that elsewhere for that particular cargo project.

Closes #38039

[rust-highfive]

r? @brson

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[japaric]

With this and #38050, following the repro steps in #38039 (comment) results in rustbuild doing no work:

$ nice $SRC_DIR/x.py build --stage 1 src/rustc --host=$HOST
    Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
Synchronizing submodule url for 'src/compiler-rt'
Synchronizing submodule url for 'src/jemalloc'
Synchronizing submodule url for 'src/liblibc'
Synchronizing submodule url for 'src/llvm'
Synchronizing submodule url for 'src/rt/hoedown'
Synchronizing submodule url for 'src/rust-installer'
HEAD is now at a8fc4c1 Merge pull request #28 from xen0n/preprocessor-firefighting
HEAD is now at e058ca6 Change how the default zone is found
HEAD is now at 6e8c1b4 Merge pull request #446 from alexcrichton/link-cfg
HEAD is now at c1d9622 Backport r285278 [ARM] Predicate UMAAL selection on hasDSP.
HEAD is now at a3736a0 Merge pull request #6 from intelfx/patch-1
HEAD is now at 4f99485 Merge pull request #54 from brson/docdir
Build completed in 0:00:02

$ tree -d build/
build/
|-- bootstrap
|   `-- debug
|       |-- build
|       |-- deps
|       |-- examples
|       `-- native
|-- cache
|   |-- 2016-09-26
|   `-- 2016-09-28
`-- x86_64-unknown-linux-gnu
    `-- stage0
        |-- bin
        |-- etc
        |   `-- bash_completion.d
        |-- lib
        |   |-- cargo
        |   `-- rustlib
        |       |-- etc
        |       `-- x86_64-unknown-linux-gnu
        |           |-- bin
        |           `-- lib
        `-- share
            |-- doc
            |   |-- cargo
            |   `-- rust
            |-- man
            |   `-- man1
            `-- zsh
                `-- site-functions

29 directories

(I haven't tried this PR in isolation)

[japaric]

(I haven't tried this PR in isolation)

Tested. Same problem.

[alexcrichton]

@japaric oh I believe this needs #37800 as well

[alexcrichton]

er #37817

[japaric]

OK. Tested again this + #37817. Using the repro instructions in #38039 (comment), now I get:

$ nice $SRC_DIR/x.py build --stage 1 src/rustc --host=$HOST
Building LLVM for x86_64-unknown-linux-gnu
Building stage0 std artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Building stage0 test artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Building stage0 compiler artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
Building stage0 std artifacts (x86_64-unknown-linux-gnu -> arm-unknown-linux-gnueabi)
Building stage0 test artifacts (x86_64-unknown-linux-gnu -> arm-unknown-linux-gnueabi)
Building LLVM for arm-unknown-linux-gnueabi
Building stage0 compiler artifacts (x86_64-unknown-linux-gnu -> arm-unknown-linux-gnueabi)

Which is better but the stage numbering seems strange:

Building stage0 compiler artifacts (x86_64-unknown-linux-gnu -> arm-unknown-linux-gnueabi)

Is this using the "snapshot" (the stage0 compiler) to build the ARM compiler? Or is it using the compiler produced by this step:

Building stage0 compiler artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

? If the former then that ^ step (or rather, the first 4 steps) wouldn't be necessary right?

EDIT: Fixed the x.py command

[alexcrichton]

Had some discussion with @japaric on IRC, and the conclusion was that if the command switches --host to --target everything works as expected, so yay!

[japaric]

r=me after #37817 lands

[japaric]

@bors r+

[bors]

📌 Commit 8e9f7f5 has been approved by japaric

[bors]

⌛ Testing commit 8e9f7f5 with merge d9aae63...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: japaric
Pushing d9aae63 to master...