x/tools: testenv.HasTool("go") gets stuck (>10m), causing test flakes [mips64le]

[gopherbot]

#!watchflakes
default <- pkg ~ `golang.org/x/tools` && output ~ `test timed out after 10m0s` && output ~ `testenv.NeedsGoPackagesEnv` && output ~ `testenv.HasTool` && goarch == "mips64le"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestExpect
panic: test timed out after 10m0s
	running tests:
		TestExpect (10m0s)

goroutine 34 [running]:
testing.(*M).startAlarm.func1()
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:2956 +0x468
created by time.goFunc
	/home/swarming/.swarming/w/ir/x/w/goroot/src/time/sleep.go:182 +0x5c
...
io.copyBuffer({0x6d3f00, 0xff9899c060}, {0x6d3e60, 0xff9898c018}, {0x0, 0x0, 0x0})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/io/io.go:411 +0xe0
io.Copy(...)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/io/io.go:388
os/exec.(*Cmd).writerDescriptor.func1()
	/home/swarming/.swarming/w/ir/x/w/goroot/src/os/exec/exec.go:613 +0x74
os/exec.(*Cmd).Start.func2(0xff989b0020)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/os/exec/exec.go:768 +0x54
created by os/exec.(*Cmd).Start in goroutine 19
	/home/swarming/.swarming/w/ir/x/w/goroot/src/os/exec/exec.go:767 +0xaa8

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "golang.org/x/tools/internal/packagestest" && test == "TestExpect"

2026-06-23 19:54 x_tools-go1.27-linux-mips64le tools@0fdde844 release-branch.go1.27@eefb4543 x/tools/internal/packagestest.TestExpect [SKIP] (log)

=== RUN   TestExpect
panic: test timed out after 10m0s
	running tests:
		TestExpect (10m0s)

goroutine 34 [running]:
testing.(*M).startAlarm.func1()
	/home/swarming/.swarming/w/ir/x/w/goroot/src/testing/testing.go:2956 +0x468
created by time.goFunc
	/home/swarming/.swarming/w/ir/x/w/goroot/src/time/sleep.go:182 +0x5c
...
io.copyBuffer({0x6d3f00, 0xff9899c060}, {0x6d3e60, 0xff9898c018}, {0x0, 0x0, 0x0})
	/home/swarming/.swarming/w/ir/x/w/goroot/src/io/io.go:411 +0xe0
io.Copy(...)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/io/io.go:388
os/exec.(*Cmd).writerDescriptor.func1()
	/home/swarming/.swarming/w/ir/x/w/goroot/src/os/exec/exec.go:613 +0x74
os/exec.(*Cmd).Start.func2(0xff989b0020)
	/home/swarming/.swarming/w/ir/x/w/goroot/src/os/exec/exec.go:768 +0x54
created by os/exec.(*Cmd).Start in goroutine 19
	/home/swarming/.swarming/w/ir/x/w/goroot/src/os/exec/exec.go:767 +0xaa8

— watchflakes

[JunyangShao]

@golang/tools-team