-output-cross-platform-c for creating a single x-platform C file

vlib/builtin/cfns.v

@@ -86,6 +86,7 @@ fn C.DEFAULT_GE() bool
 fn C.isatty() int
 
 fn C.syscall() int
+fn C.sysctl() int
 
 
 

vlib/compiler/comptime.v

@@ -34,7 +34,9 @@ fn (p mut Parser) comp_time() {
 			}
 			p.check(.lcbr)
 			os := os_from_string(name)
-			if (!not && os != p.os) || (not && os == p.os) {
+			if ((!not && os != p.os) || (not && os == p.os)) &&
+				!p.pref.output_cross_c
+			{
 				// `$if os {` for a different target, skip everything inside
 				// to avoid compilation errors (like including <windows.h>
 				// on non-Windows systems)

vlib/compiler/main.v

@@ -129,6 +129,7 @@ pub mut:
 	vlib_path string
 	vpath string
 	x64 bool
+	output_cross_c bool
 }
 
 // Should be called by main at the end of the compilation process, to cleanup
@@ -1042,6 +1043,7 @@ pub fn new_v(args[]string) &V {
 		fast: '-fast' in args
 		is_bare: '-freestanding' in args
 		x64: '-x64' in args
+		output_cross_c: '-output-cross-platform-c' in args
 		is_repl: is_repl
 		build_mode: build_mode
 		cflags: cflags