Auto merge of #53190 - sekineh:thumb-cortex-m, r=jamesmunns

Add crate build test for `thumb*` targets. [IRR-2018-embedded]

## Summary

This PR adds `run-make` test that compiles `cortex-m` crate for all supported `thumb*-none-*` targets using `cargo` and stage2 `rustc`.

- Supported `thumb*-none-*` targets:
  - thumbv6m-none-eabi (Bare Cortex-M0, M0+, M1)
  - thumbv7em-none-eabi (Bare Cortex-M4, M7)
  - thumbv7em-none-eabihf (Bare Cortex-M4F, M7F, FPU, hardfloat)
  - thumbv7m-none-eabi (Bare Cortex-M3)

## How to run & Example output
I tested locally and all targets succeeded like below:
```
./x.py clean
./x.py test --target thumbv6m-none-eabi,thumbv7em-none-eabi,thumbv7em-none-eabihf,thumbv7m-none-eabi src/test/run-make
```
```
Check compiletest suite=run-make mode=run-make (x86_64-unknown-linux-gnu -> thumbv6m-none-eabi)

running 5 tests
.....
test result: ok. 5 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
```

## How to re-run

Remove `stamp` file for the test run.
```
rm build/x86_64-unknown-linux-gnu/test/run-make/thumb-none-cortex-m/stamp
```
Then run `test`
```
./x.py test --target thumbv6m-none-eabi,thumbv7em-none-eabi,thumbv7em-none-eabihf,thumbv7m-none-eabi src/test/run-make
(snip)
running 5 tests
iiii.
test result: ok. 1 passed; 0 failed; 4 ignored; 0 measured; 0 filtered out
```

## Artifacts

You can examine the artifacts under the directory below:
```
sekineh@sekineh-VirtualBox:~/rustme10$ ls -l build/x86_64-unknown-linux-gnu/test/run-make/thumb-none-cortex-m/thumb-none-cortex-m/
total 4
drwxrwxr-x 7 sekineh sekineh 4096  8月 14 22:40 cortex-m
```
where `build/x86_64-unknown-linux-gnu/test/run-make/thumb-none-cortex-m/thumb-none-cortex-m/` is came from TMPDIR variable.

## Other notes

For `test.rs` modification, I used the same logic as:
- https://github.com/rust-lang/rust/blame/d8b3c830fbcdd14d085209a8dcc3399151f3286a/src/bootstrap/dist.rs#L652-L657
```
            if builder.no_std(target) == Some(true) {
                // the `test` doesn't compile for no-std targets
                builder.ensure(compile::Std { compiler, target });
            } else {
                builder.ensure(compile::Test { compiler, target });
            }
```
It is a useful snippet when adding `no_std` support to `src/bootstrap` code.

CC @kennytm @jamesmunns @nerdyvaishali

src/bootstrap/test.rs

@@ -975,9 +975,19 @@ impl Step for Compiletest {
             builder.ensure(compile::Rustc { compiler, target });
         }
 
-        if builder.no_std(target) != Some(true) {
+        if builder.no_std(target) == Some(true) {
+            // the `test` doesn't compile for no-std targets
+            builder.ensure(compile::Std { compiler, target });
+        } else {
             builder.ensure(compile::Test { compiler, target });
         }
+
+        if builder.no_std(target) == Some(true) {
+            // for no_std run-make (e.g. thumb*),
+            // we need a host compiler which is called by cargo.
+            builder.ensure(compile::Std { compiler, target: compiler.host });
+        }
+
         builder.ensure(native::TestHelpers { target });
         builder.ensure(RemoteCopyLibs { compiler, target });
 

src/test/run-make/git_clone_sha1.sh

@@ -0,0 +1,33 @@
+#!/bin/bash -x
+
+# Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+# Usage: $0 project_name url sha1
+# Get the crate with the specified sha1.
+#
+# all arguments are required.
+#
+# See below link for git usage:
+# https://stackoverflow.com/questions/3489173#14091182
+
+# Mandatory arguments:
+PROJECT_NAME=$1
+URL=$2
+SHA1=$3
+
+function err_exit() {
+    echo "ERROR:" $*
+    exit 1
+}
+
+git clone $URL $PROJECT_NAME || err_exit
+cd $PROJECT_NAME || err_exit
+git reset --hard $SHA1 || err_exit

src/test/run-make/thumb-none-cortex-m/Makefile

@@ -0,0 +1,38 @@
+-include ../../run-make-fulldeps/tools.mk
+
+# How to run this
+# $ ./x.py clean
+# $ ./x.py test --target thumbv6m-none-eabi,thumbv7m-none-eabi src/test/run-make
+
+# Supported targets:
+# - thumbv6m-none-eabi (Bare Cortex-M0, M0+, M1)
+# - thumbv7em-none-eabi (Bare Cortex-M4, M7)
+# - thumbv7em-none-eabihf (Bare Cortex-M4F, M7F, FPU, hardfloat)
+# - thumbv7m-none-eabi (Bare Cortex-M3)
+
+# See https://stackoverflow.com/questions/7656425/makefile-ifeq-logical-or
+ifneq (,$(filter $(TARGET),thumbv6m-none-eabi thumbv7em-none-eabi thumbv7em-none-eabihf thumbv7m-none-eabi))
+
+# For cargo setting
+RUSTC := $(RUSTC_ORIGINAL)
+LD_LIBRARY_PATH := $(HOST_RPATH_DIR)
+# We need to be outside of 'src' dir in order to run cargo
+WORK_DIR := $(TMPDIR)
+
+HERE := $(shell pwd)
+
+CRATE := cortex-m
+CRATE_URL := https://github.com/rust-embedded/cortex-m
+CRATE_SHA1 := a448e9156e2cb1e556e5441fd65426952ef4b927 # 0.5.0
+
+all:
+	env
+	mkdir -p $(WORK_DIR)
+	-cd $(WORK_DIR) && rm -rf $(CRATE)
+	cd $(WORK_DIR) && bash -x $(HERE)/../git_clone_sha1.sh $(CRATE) $(CRATE_URL) $(CRATE_SHA1)
+	cd $(WORK_DIR) && cd $(CRATE) && $(CARGO) build --target $(TARGET) -v
+else
+
+all:
+
+endif