Go 1.26 added syscall.runtimeClearenv (called by syscall.Clearenv) which
must be provided by the runtime via go:linkname. Without it, the os
package fails to link.
This adds true GOOS=wasip1 support in addition to our existing
-target=wasi support. The old support for WASI isn't removed, but should
be treated as deprecated and will likely be removed eventually to reduce
the test burden.
Jake Bailey
deadprogram
Ayke van Laethem