Improve build times on non-x86 systems

Signed-off-by: Alexander F. Lent <lx@xanderlent.com>

python-torch.spec

@@ -506,10 +506,15 @@ sed -i -e 's@${PROJECT_SOURCE_DIR}/third_party/concurrentqueue@/usr/include/conc
 # Control the number of jobs
 #
 # The build can fail if too many threads exceed the physical memory
-# So count core and and memory and increase the build memory util the build succeeds
+# Run at least one thread, more if CPU & memory resources are available.
 #
+%ifarch x86_64
 # Real cores, No hyperthreading
 COMPILE_JOBS=`cat /proc/cpuinfo | grep -m 1 'cpu cores' | awk '{ print $4 }'`
+%else
+# cpuinfo format varies on other arches, fall back to nproc
+COMPILE_JOBS=`nproc`
+%endif
 if [ ${COMPILE_JOBS}x = x ]; then
     COMPILE_JOBS=1
 fi