Fix compiling libstd with emscripten target.

[ashleysommer]

Was getting error:

running: "sh" "/home/flubba86/rust/src/libstd/../libbacktrace/configure" "--with-pic" "--disable-multilib" "--disable-shared" "--disable-host-shared" "--host=asmjs-unknown-emscripten" "--build=x86_64-unknown-linux-gnu"
...
Invalid configuration `asmjs-unknown-emscripten': system `emscripten' not recognized

This commit adds the emscripten target to the libbacktrace configure script so it is no longer unrecognized.

[rust-highfive]

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[alexcrichton]

This is actually code that we don't ourselves control because it comes from upstream, but we also shouldn't try to compile libbacktrace when compiling for emscripten. Could you elaborate on how you ran into this error?

[ashleysommer]

Just doing cargo build --target=asmjs-unknown-emscripten --release in the libstd directory.
Full error:

flubba86@localhost:~/rust/src/libstd$ /usr/local/rustjs/bin/cargo build --target=asmjs-unknown-emscripten --release
Adding directories to PATH:
PATH += /mnt/mint/home/flubba86/Downloads/emsdk_portable
PATH += /mnt/mint/home/flubba86/Downloads/emsdk_portable/emscripten/incoming

Setting environment variables:
EM_CONFIG = /home/flubba86/.emscripten
EMSCRIPTEN = /mnt/mint/home/flubba86/Downloads/emsdk_portable/emscripten/incoming

   Compiling gcc v0.3.25
   Compiling libc v0.0.0 (file:///home/flubba86/rust/src/libstd)
   Compiling build_helper v0.1.0 (file:///home/flubba86/rust/src/libstd)
   Compiling core v0.0.0 (file:///home/flubba86/rust/src/libstd)
   Compiling std v0.0.0 (file:///home/flubba86/rust/src/libstd)
Build failed, waiting for other jobs to finish...
failed to run custom build command for `std v0.0.0 (file:///home/flubba86/rust/src/libstd)`
Process didn't exit successfully: `/home/flubba86/rust/src/libstd/target/release/build/std-f43ff7732835f762/build-script-build` (exit code: 1)
--- stdout
cargo:rustc-cfg=cargobuild
cargo:rustc-link-lib=static=backtrace
cargo:rustc-link-search=native=/home/flubba86/rust/src/libstd/target/asmjs-unknown-emscripten/release/build/std-f43ff7732835f762/out/.libs
OPT_LEVEL = Some("3")
PROFILE = Some("release")
TARGET = Some("asmjs-unknown-emscripten")
debug=false opt-level=3
HOST = Some("x86_64-unknown-linux-gnu")
TARGET = Some("asmjs-unknown-emscripten")
TARGET = Some("asmjs-unknown-emscripten")
HOST = Some("x86_64-unknown-linux-gnu")
CC_asmjs-unknown-emscripten = None
CC_asmjs_unknown_emscripten = None
TARGET_CC = None
CC = None
HOST = Some("x86_64-unknown-linux-gnu")
TARGET = Some("asmjs-unknown-emscripten")
HOST = Some("x86_64-unknown-linux-gnu")
CFLAGS_asmjs-unknown-emscripten = None
CFLAGS_asmjs_unknown_emscripten = None
TARGET_CFLAGS = None
CFLAGS = None
running: "sh" "/home/flubba86/rust/src/libstd/../libbacktrace/configure" "--with-pic" "--disable-multilib" "--disable-shared" "--disable-host-shared" "--host=asmjs-unknown-emscripten" "--build=x86_64-unknown-linux-gnu"
checking build system type... x86_64-unknown-linux-gnu
checking host system type... 

command did not execute successfully: "sh" "/home/flubba86/rust/src/libstd/../libbacktrace/configure" "--with-pic" "--disable-multilib" "--disable-shared" "--disable-host-shared" "--host=asmjs-unknown-emscripten" "--build=x86_64-unknown-linux-gnu"
expected success, got: exit code: 1



--- stderr
Invalid configuration `asmjs-unknown-emscripten': system `emscripten' not recognized
configure: error: /bin/sh /home/flubba86/rust/src/libstd/../libbacktrace/config.sub asmjs-unknown-emscripten failed

[alexcrichton]

Aha I had a feeling this might be using rustbuild...

Anyway, using cargo is not currently a supported build system for all targets which is why this isn't working. The main build system disables compiling libbacktrace for emscripten, and we just need to update src/libstd/build.rs to do the same. Could you retarget this patch to that file instead?

[ashleysommer]

Thanks for the clarification. I restored libbacktrace/config.sub back to how it was, and added an additional compile-time check to libstd/build.rs to not compile libbacktrace during a rustbuild of libstd.

[alexcrichton]

Thanks! Can you also squash the commits together?

[ashleysommer]

So now I know how to squash commits in a pull-request :)

[alexcrichton]

@bors: r+ d846f49