Build script:

* Use sudo with CentOS versions repo editing to make the logic consistent.
* Set make concurrency equal to the number of logical CPUs on MacOS X.

travis/script.sh

@@ -239,19 +239,19 @@ build_centos()
 {
     if [ x"$1" = x'5' ]; then
         # Centos 5 EOL, use vault for now.
-        sed -i 's/enabled=1/enabled=0/' \
+        $MYSUDO sed -i 's/enabled=1/enabled=0/' \
             /etc/yum/pluginconf.d/fastestmirror.conf
-        sed -i 's/mirrorlist/#mirrorlist/' \
+        $MYSUDO sed -i 's/mirrorlist/#mirrorlist/' \
             /etc/yum.repos.d/*.repo
-        sed -i 's/#\(baseurl.*\)mirror.centos.org\/centos\/\$releasever\//\1vault.centos.org\/5.11\//' \
+        $MYSUDO sed -i 's/#\(baseurl.*\)mirror.centos.org\/centos\/\$releasever\//\1vault.centos.org\/5.11\//' \
             /etc/yum.repos.d/*.repo
     elif [ x"$1" = x'6' ]; then
         # Centos 6 EOL, use vault for now.
-        sed -i 's/enabled=1/enabled=0/' \
+        $MYSUDO sed -i 's/enabled=1/enabled=0/' \
             /etc/yum/pluginconf.d/fastestmirror.conf
-        sed -i 's/mirrorlist/#mirrorlist/' \
+        $MYSUDO sed -i 's/mirrorlist/#mirrorlist/' \
             /etc/yum.repos.d/*.repo
-        sed -i 's/#\(baseurl.*\)mirror.centos.org\/centos\/\$releasever\//\1vault.centos.org\/6.10\//' \
+        $MYSUDO sed -i 's/#\(baseurl.*\)mirror.centos.org\/centos\/\$releasever\//\1vault.centos.org\/6.10\//' \
             /etc/yum.repos.d/*.repo
     elif [ x"$1" = x'7' ]; then
         # Centos 7 EOL, use vault for now.
@@ -407,7 +407,9 @@ elif [ x"$BUILD_OS_NAME" = x'osx' ]; then
     make rat clean
     sysctl machdep.cpu || true
     df -h || true
-    do_build -j 2
+    cpu_count=$(sysctl -n hw.ncpu)
+    expr "$cpu_count" : '^[0-9]*$' > /dev/null || cpu_count=2
+    do_build -j "$cpu_count"
 else
     echo "OS: $BUILD_OS_NAME not yet supported"
     exit 1