Bug 1570224 - Use nproc instead of getconf _NPROCESSORS_ONLN. r=nalexander

Plenty of places use `nproc`, and only a couple use `getconf
_NPROCESSORS_ONLN`. Use the former instead of the latter.

Differential Revision: https://phabricator.services.mozilla.com/D39999

--HG--
extra : moz-landing-system : lando

build/unix/build-hfsplus/build-hfsplus.sh

@@ -10,7 +10,7 @@ set -x
 hfplus_version=540.1.linux3
 md5sum=0435afc389b919027b69616ad1b05709
 filename=diskdev_cmds-${hfplus_version}.tar.gz
-make_flags="-j$(getconf _NPROCESSORS_ONLN)"
+make_flags="-j$(nproc)"
 
 root_dir="$1"
 if [ -z "$root_dir" -o ! -d "$root_dir" ]; then

taskcluster/scripts/misc/build-libdmg-hfsplus.sh

@@ -13,7 +13,7 @@ mkdir -p $UPLOAD_DIR $STAGE
 cd $MOZ_FETCHES_DIR/libdmg-hfsplus
 
 cmake -DOPENSSL_USE_STATIC_LIBS=1 .
-make -j$(getconf _NPROCESSORS_ONLN)
+make -j$(nproc)
 
 # We only need the dmg and hfsplus tools.
 strip dmg/dmg hfs/hfsplus