Define environment variable TMP as an alias for TEMP.

diff --git a/files/directory.c b/files/directory.c
index 9dc7aff..6d64d2b 100644
--- a/files/directory.c
+++ b/files/directory.c
@@ -129,6 +129,7 @@
 
     SetEnvironmentVariableA( "PATH", path );
     SetEnvironmentVariableA( "TEMP", tmp_dir.short_name );
+    SetEnvironmentVariableA( "TMP", tmp_dir.short_name );
     SetEnvironmentVariableA( "windir", DIR_Windows.short_name );
     SetEnvironmentVariableA( "winsysdir", DIR_System.short_name );