pref,os,sokol,cgen: ease compilation of 2048 with -os wasm32_emscripten (#15820)

vlib/os/os.c.v

@@ -901,7 +901,9 @@ pub fn fork() int {
 pub fn wait() int {
 	mut pid := -1
 	$if !windows {
-		pid = C.wait(0)
+		$if !emscripten ? {
+			pid = C.wait(0)
+		}
 	}
 	$if windows {
 		panic('os.wait not supported in windows') // TODO

vlib/os/os_nix.c.v

@@ -8,7 +8,7 @@ import strings
 #include <sys/utsname.h>
 #include <sys/types.h>
 #include <utime.h>
-$if !solaris && !haiku {
+$if !solaris && !haiku && !emscripten ? {
 	#include <sys/ptrace.h>
 }
 

vlib/os/process_nix.c.v

@@ -75,7 +75,10 @@ fn (mut p Process) unix_kill_pgroup() {
 
 fn (mut p Process) unix_wait() {
 	cstatus := 0
-	ret := C.waitpid(p.pid, &cstatus, 0)
+	mut ret := -1
+	$if !emscripten ? {
+		ret = C.waitpid(p.pid, &cstatus, 0)
+	}
 	if ret == -1 {
 		p.err = posix_get_error_msg(C.errno)
 		return
@@ -92,7 +95,10 @@ fn (mut p Process) unix_wait() {
 
 fn (mut p Process) unix_is_alive() bool {
 	cstatus := 0
-	ret := C.waitpid(p.pid, &cstatus, C.WNOHANG)
+	mut ret := -1
+	$if !emscripten ? {
+		ret = C.waitpid(p.pid, &cstatus, C.WNOHANG)
+	}
 	if ret == -1 {
 		p.err = posix_get_error_msg(C.errno)
 		return false