audio/musepack-tools: Force a single make job.

Signed-off-by: Matteo Bernardini <ponce@slackbuilds.org>

audio/musepack-tools/musepack-tools.SlackBuild

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-# Slackware build script for libreplaygain
+# Slackware build script for musepack-tools
 # Written by Šime Ramov <s@ramov.com>
 
 PRGNAM=musepack-tools
@@ -61,7 +61,7 @@ cd build
     -DCMAKE_INSTALL_PREFIX=/usr \
     -DLIB_SUFFIX=$LIBDIRSUFFIX \
     -DCMAKE_BUILD_TYPE=Release ..
-  make
+  make -j1
   make install DESTDIR=$PKG
 cd ..