runtime.getcaller{pc,sp} expect their argument to be a pointer to the
caller's first function argument. This assumption breaks when the caller
is inlined. For example, with -l=4, calls to runtime.entersyscall (which
calls getcallerpc) are inlined and that breaks multiple cgo tests.

This change modifies the compiler to refuse to inline functions that
call runtime.getcaller{pc,sp}. Alternatively, we could mark these
functions //go:noinline but that limits optimization opportunities if
the calls to getcaller{pc,sp} are eliminated as dead code.

Previously TestCgoPprofPIE, TestCgoPprof, and TestCgoCallbackGC failed
with -l=4. Now all of the runtime tests pass with -l=4.

Change-Id: I258bca9025e20fc451e673a18f862b5da1e07ae7
Reviewed-on: https://go-review.googlesource.com/40998
Run-TryBot: David Lazar <lazard@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Austin Clements <austin@google.com>