gc: drop support for 'precise' globals

Precise globals require a whole program optimization pass that is hard
to support when building packages separately. This patch removes support
for these globals by converting the last use (Linux) to use
linker-defined symbols instead.

For details, see: https://github.com/tinygo-org/tinygo/issues/2870

src/runtime/os_other.go

@@ -0,0 +1,11 @@
+//go:build linux && (baremetal || nintendoswitch || wasi)
+// +build linux
+// +build baremetal nintendoswitch wasi
+
+// Other systems that aren't operating systems supported by the Go toolchain
+// need to pretend to be an existing operating system. Linux seems like a good
+// choice for this for its wide hardware support.
+
+package runtime
+
+const GOOS = "linux"