cmd/compile: panic due to undocumented `gotypesalias` GODEBUG in types2

[gopherbot]

#!watchflakes
post <- log ~ `Value of name not listed in godebugs.All: gotypesalias`

Issue created automatically to collect these failures.

Example (log):

<unknown line number>: internal compiler error: panic: godebug: Value of name not listed in godebugs.All: gotypesalias

goroutine 1 [running]:
runtime/debug.Stack()
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/runtime/debug/stack.go:24 +0x6c
bootstrap/cmd/compile/internal/base.FatalfAt({0x1ea74?, 0x0?}, {0x72baa9, 0x9}, {0x881d0db8, 0x1, 0x1})
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:225 +0x23c
bootstrap/cmd/compile/internal/base.Fatalf(...)
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:194
bootstrap/cmd/compile/internal/gc.handlePanic()
...
<unknown line number>: internal compiler error: panic: godebug: Value of name not listed in godebugs.All: gotypesalias

goroutine 1 [running]:
runtime/debug.Stack()
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/runtime/debug/stack.go:24 +0x6c
bootstrap/cmd/compile/internal/base.FatalfAt({0x1ea74?, 0x0?}, {0x72baa9, 0x9}, {0x882f6db8, 0x1, 0x1})
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:225 +0x23c
bootstrap/cmd/compile/internal/base.Fatalf(...)
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:194
bootstrap/cmd/compile/internal/gc.handlePanic()
...
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- repo == "oauth2" && section == "Building Go bootstrap cmd/go (go_bootstrap) using Go toolchain1." && test == ""

2023-11-08 20:28 freebsd-riscv64-unmatched oauth2@e067960a go@30de0b5e (log)

<unknown line number>: internal compiler error: panic: godebug: Value of name not listed in godebugs.All: gotypesalias

goroutine 1 [running]:
runtime/debug.Stack()
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/runtime/debug/stack.go:24 +0x6c
bootstrap/cmd/compile/internal/base.FatalfAt({0x1ea74?, 0x0?}, {0x72baa9, 0x9}, {0x881d0db8, 0x1, 0x1})
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:225 +0x23c
bootstrap/cmd/compile/internal/base.Fatalf(...)
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:194
bootstrap/cmd/compile/internal/gc.handlePanic()
...
<unknown line number>: internal compiler error: panic: godebug: Value of name not listed in godebugs.All: gotypesalias

goroutine 1 [running]:
runtime/debug.Stack()
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/runtime/debug/stack.go:24 +0x6c
bootstrap/cmd/compile/internal/base.FatalfAt({0x1ea74?, 0x0?}, {0x72baa9, 0x9}, {0x882f6db8, 0x1, 0x1})
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:225 +0x23c
bootstrap/cmd/compile/internal/base.Fatalf(...)
	/tmp/workdir-host-freebsd-riscv64-unmatched/go/src/cmd/compile/internal/base/print.go:194
bootstrap/cmd/compile/internal/gc.handlePanic()
...
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory
go tool dist: open /tmp/workdir-host-freebsd-riscv64-unmatched/go/pkg/freebsd_riscv64: no such file or directory

— watchflakes

[bcmills]

Fixed by https://go.dev/cl/542135