utils.py: add parallel make helpers

The code to extract the integer number of parallel build threads and
construct a new argument from them has started to be copied in multiple
locations, so create two new helper utilities to aid recipes.

The first helper (parallel_make()) extracts the integer number of
parallel build threads from PARALLEL_MAKE. The second
(parallel_make_argument()) does the same and then puts the result back
into a format string, optionally clamping it to some maximum value.

Additionally, rework the oe-core recipes that were manually doing this
to use the new helper utilities.

(From OE-Core rev: ccd1142d22b31ed85d8823b1bc9e11ccfd72b61f)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-support/boost/boost.inc

@@ -135,29 +135,7 @@ BJAM_TOOLS   = "--ignore-site-config \
 
 # use PARALLEL_MAKE to speed up the build, but limit it by -j 64, greater parallelism causes bjam to segfault or to ignore -j
 # https://svn.boost.org/trac/boost/ticket/7634
-def get_boost_parallel_make(d):
-    pm = d.getVar('PARALLEL_MAKE')
-    if pm:
-        # look for '-j' and throw other options (e.g. '-l') away
-        # because they might have different meaning in bjam
-        pm = pm.split()
-        while pm:
-            v = None
-            opt = pm.pop(0)
-            if opt == '-j':
-                v = pm.pop(0)
-            elif opt.startswith('-j'):
-                v = opt[2:].strip()
-            else:
-                v = None
-
-            if v:
-                v = min(64, int(v))
-                return '-j' + str(v)
-
-    return ""
-
-BOOST_PARALLEL_MAKE = "${@get_boost_parallel_make(d)}"
+BOOST_PARALLEL_MAKE = "${@oe.utils.parallel_make_argument(d, '-j%d', limit=64)}"
 BJAM_OPTS    = '${BOOST_PARALLEL_MAKE} -d+2 -q \
 		${BJAM_TOOLS} \
 		-sBOOST_BUILD_USER_CONFIG=${WORKDIR}/user-config.jam \