make junit output more consistent with default format

[yaahc]

The default format of libtest includes new-lines between each section to ensure the label output from cargo is on it's own line

❯ cargo test
 Compiling test-test v0.1.0 (/home/jlusby/tmp/test-test)
 Finished test [unoptimized + debuginfo] target(s) in 0.59s
 Running unittests (target/debug/deps/test_test-639f369234319c09)
running 1 test
test tests::it_works ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
 Doc-tests test-test
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

But when the junit outputter was added to libtest these newlines were omitted, resulting in some "fun" output when run via cargo.

Note the Doc-tests text at the end of the first line of xml.

❯ cargo test -- -Zunstable-options --format junit
 Finished test [unoptimized + debuginfo] target(s) in 0.00s
 Running unittests (target/debug/deps/test_test-639f369234319c09)
<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="0" tests="1" skipped="0" ><testcase classname="tests" name="it_works" time="0"/><system-out/><system-err/></testsuite></testsuites> Doc-tests test-test
<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="0" tests="0" skipped="0" ><system-out/><system-err/></testsuite></testsuites>

After this PR the junit output includes the same style of newlines as the pretty format

❯ cargo test -- -Zunstable-options --format junit
 Compiling test-test v0.1.0 (/home/jlusby/tmp/test-test)
 Finished test [unoptimized + debuginfo] target(s) in 0.39s
 Running unittests (target/debug/deps/test_test-42c2320bb9450c69)
<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="0" tests="1" skipped="0" ><testcase classname="tests" name="it_works" time="0"/><system-out/><system-err/></testsuite></testsuites>
 Doc-tests test-test
<?xml version="1.0" encoding="UTF-8"?><testsuites><testsuite name="test" package="test" id="0" errors="0" failures="0" tests="0" skipped="0" ><system-out/><system-err/></testsuite></testsuites>

[rust-highfive]

r? @Mark-Simulacrum

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[yaahc]

r? rust-lang/libs

[yaahc]

@andoriyu since you authored the original junit PR I wanted to double check with you that the newlines I'm adding don't mess with any of your original design goals. I know there's the assert against newlines in write_message and I assumed that was to prevent newlines in the middle of the xml output. I figured that it would however be fine to include extra newlines before and after.

[andoriyu]

@andoriyu since you authored the original junit PR I wanted to double check with you that the newlines I'm adding don't mess with any of your original design goals. I know there's the assert against newlines in write_message and I assumed that was to prevent newlines in the middle of the xml output. I figured that it would however be fine to include extra newlines before and after.

I think adding newlines is fine.

[kennytm]

r=me but i think we could use b"…" instead of "…".aṡ_bytes().

[kennytm]

@bors r+ rollup

[bors]

📌 Commit 0911069 has been approved by kennytm