system/ti99sim: Fix build when ARCH is set in the environment.

Signed-off-by: B. Watson <urchlay@slackware.uk>

Signed-off-by: Willy Sudiarto Raharjo <willysr@slackbuilds.org>

system/ti99sim/ti99sim.SlackBuild

@@ -70,7 +70,7 @@ sed -i "s,-g3  *-O3,$SLKCFLAGS," rules.mak
 
 # Binaries already installed stripped. SYS_BIN must be <DATA_DIR>/bin
 # to avoid it creating absolute symlinks (we'll create relative ones, below).
-make install DATA_DIR=$PKG/opt/$PRGNAM SYS_BIN=$PKG/opt/$PRGNAM/bin
+env -u ARCH make install DATA_DIR=$PKG/opt/$PRGNAM SYS_BIN=$PKG/opt/$PRGNAM/bin
 
 # Modified setup script requires arguments (original one didn't).
 sh scripts/setup $CWD $PKG/opt/$PRGNAM