add framework to support archs without a native wait4 syscall

this commit should make no codegen change for existing archs, but is a
prerequisite for new archs including riscv32. the wait4 emulation
backend provides both cancellable and non-cancellable variants because
waitpid is required to be a cancellation point, but all of our other
uses are not, and most of them cannot be.

based on patch by Stefan O'Rear.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/process/waitpid.c b/src/process/waitpid.c
index 1b65bf05..80231862 100644
--- a/src/process/waitpid.c
+++ b/src/process/waitpid.c
@@ -3,5 +3,5 @@
 
 pid_t waitpid(pid_t pid, int *status, int options)
 {
-	return syscall_cp(SYS_wait4, pid, status, options, 0);
+	return sys_wait4_cp(pid, status, options, 0);
 }