Android: do not re-export macros from linux/stat.h from other modules

This lets us declare constants in the Android platform module using the expected mode_t type

Author: hyp

stdlib/public/Platform/Platform.swift

@@ -241,7 +241,7 @@ public var S_IFIFO: Int32 { return Int32(0x1000) }
 public var S_IREAD: Int32  { return Int32(0x0100) }
 public var S_IWRITE: Int32 { return Int32(0x0080) }
 public var S_IEXEC: Int32  { return Int32(0x0040) }
-#elseif !os(Android)
+#else
 public var S_IFMT: mode_t   { return mode_t(0o170000) }
 public var S_IFIFO: mode_t  { return mode_t(0o010000) }
 public var S_IFCHR: mode_t  { return mode_t(0o020000) }