haiku support (part 2)

vlib/compiler/cc.v

@@ -263,8 +263,8 @@ fn (v mut V) cc() {
 	a << libs
 	// Without these libs compilation will fail on Linux
 	// || os.user_os() == 'linux'
-	if !v.pref.is_bare && v.pref.build_mode != .build_module && (v.os == .linux || v.os == .freebsd || v.os == .openbsd ||
-		v.os == .netbsd || v.os == .dragonfly || v.os == .solaris) {
+	if !v.pref.is_bare && v.pref.build_mode != .build_module && v.os in [ .linux, .freebsd,
+		.openbsd, .netbsd, .dragonfly, .solaris, .haiku ] {
 		a << '-lm -lpthread '
 		// -ldl is a Linux only thing. BSDs have it in libc.
 		if v.os == .linux {

vlib/compiler/main.v

@@ -966,6 +966,9 @@ pub fn new_v(args[]string) &V {
 		$if solaris {
 			_os = .solaris
 		}
+		$if haiku {
+			_os = .haiku
+		}
 	}
 	else {
 		_os = os_from_string(target_os)
@@ -1149,6 +1152,7 @@ pub fn os_from_string(os string) OS {
 			// notice that `-os msvc` became `-cc msvc`
 			verror('use the flag `-cc msvc` to build using msvc')
 		}
+		'haiku' { return .haiku }
 	}
 	println('bad os $os') // todo panic?
 	return .linux

vlib/os/os.v

@@ -697,6 +697,9 @@ pub fn user_os() string {
 	$if solaris {
 		return 'solaris'
 	}
+	$if haiku {
+		return 'haiku'
+	}
 	return 'unknown'
 }
 
@@ -796,6 +799,8 @@ pub fn executable() string {
 	}
 	$if solaris {
 	}
+	$if haiku {
+	}
 	$if netbsd {
 		mut result := calloc(MAX_PATH)
 		count := int(C.readlink('/proc/curproc/exe', result, MAX_PATH ))