Rollup merge of #131705 - hoodmane:fix-emscripten-tests, r=jieyouxu

Fix most ui tests on emscripten target

To fix the linker errors, we need to set the output extension to `.js` instead of `.wasm`. Setting the output to a `.wasm` file puts Emscripten into standalone mode which is effectively a distinct target. We need to set the runner to be `node` as well.

This fixes most of the ui tests. I fixed 4 additional tests with simple problems:

- `intrinsics/intrinsic-alignment.rs` -- Two `#[cfg]` macros match for Emscripten so we got duplicate definition
- `structs-enums/rec-align-u64.rs` -- same problem
- `issues/issue-12699.rs` -- hangs so I disabled it
- `process/process-sigpipe.rs` -- Not expected to work on Emscripten so I disabled it

Resolves #131666.

There are 7 more failing tests. I'll try to investigate more and see if I can fix them or at least understand why they happen.

- abi/numbers-arithmetic/return-float.rs (problem with [wasm treatment of noncanonical floats](https://webassembly.github.io/spec/core/exec/numerics.html#nan-propagation)?)
- async-await/issue-60709.rs -- linker error related to memcpy. Possible Emscripten bug?
- backtrace/dylib-dep.rs -- Says "Not supported"
- backtrace/line-tables-only.rs -- Says "Not supported"
- no_std/no-std-unwind-binary.rs -- compiler says `error: lang item required, but not found: eh_catch_typeinfo`
- structs-enums/enum-rec/issue-17431-6.rs -- One of the two compiler errors is missing
- test-attrs/test-passed.rs

    r?workingjubilee r?jieyouxu

src/tools/compiletest/src/runtest.rs

@@ -1643,7 +1643,9 @@ impl<'test> TestCx<'test> {
         // double the length.
         let mut f = self.output_base_dir().join("a");
         // FIXME: This is using the host architecture exe suffix, not target!
-        if self.config.target.starts_with("wasm") {
+        if self.config.target.contains("emscripten") {
+            f = f.with_extra_extension("js");
+        } else if self.config.target.starts_with("wasm") {
             f = f.with_extra_extension("wasm");
         } else if self.config.target.contains("spirv") {
             f = f.with_extra_extension("spv");

src/tools/tidy/src/issues.txt

@@ -1520,7 +1520,6 @@ ui/issues/issue-12567.rs
 ui/issues/issue-12612.rs
 ui/issues/issue-12660.rs
 ui/issues/issue-12677.rs
-ui/issues/issue-12699.rs
 ui/issues/issue-12729.rs
 ui/issues/issue-12744.rs
 ui/issues/issue-12860.rs

src/tools/tidy/src/ui_tests.rs

@@ -17,7 +17,7 @@ use ignore::Walk;
 const ENTRY_LIMIT: u32 = 901;
 // FIXME: The following limits should be reduced eventually.
 
-const ISSUES_ENTRY_LIMIT: u32 = 1673;
+const ISSUES_ENTRY_LIMIT: u32 = 1672;
 
 const EXPECTED_TEST_FILE_EXTENSIONS: &[&str] = &[
     "rs",     // test source files