std/time: use sys package for environment variable lookup

std/time/zoneinfo_unix.jule

@@ -7,10 +7,7 @@
 // See tzfile(5), https://en.wikipedia.org/wiki/Zoneinfo,
 // and ftp://munnari.oz.au/pub/oldtz/
 
-use integ "std/jule/integrated"
-
-cpp unsafe fn getenv(name: *integ::Char): *integ::Char
-cpp unsafe fn setenv(name: *integ::Char, value: *integ::Char, overwrite: int): int
+use "std/sys"
 
 // Many systems use /usr/share/zoneinfo, Solaris 2 has
 // /usr/share/lib/zoneinfo, IRIX 6 has /usr/lib/locale/TZ,
@@ -31,7 +28,7 @@ fn initLocal() {
 	// /usr/share/zoneinfo/foo will be used.
 
 	mut tz := "TZ\000"
-	tz = unsafe { integ::BytePtrToStr((*byte)(cpp.getenv((*integ::Char)(&tz[0])))) }
+	tz, _ = unsafe { sys::Getenv(&tz[0]) }
 	match {
 	| len(tz) == 0:
 		mut z, ok := loadLocation("localtime", ["/etc"])