use ccache for cross compilation

[kived]

ccache is already used for building hostpython (if /usr/lib/ccache is added to the PATH), but not for any cross compiles.

This adds ccache to the CC and CXX env vars for standard and Cython builds, and sets NDK_CCACHE to the ccache binary for NDK builds. ccache usage is enabled by default, for convenience, but will respect the USE_CCACHE var (if set to 0, ccache will not be used).

My distribution

• recipes: hostpython2, jpeg, libffi, openssl, png, sdl2_image, sdl2_mixer, sdl2_ttf, python2, cdecimal, cnotify, eesentinel, enum34, evdev, ipaddress, pil, pyasn1, pycrypto, pytz, pyusb, sdl2, setuptools, six, zope_event, zope_interface, babel, gryphus, idna, pycparser, pyjnius, pyopenssl, sqlalchemy, twisted, zope_component, cffi, kivy, cryptography, aeris2, which includes some custom recipes
• pure python: pyasn1_modules, alembic, characteristic, bitstring, qrcode, service_identity, tenjin, pymysql, phonenumbers, mako

For this distribution, these changes greatly decreased my rebuild time. Tested with deleting build and dists, but leaving packages alone to keep the download cache, then rebuilding the entire distribution as well as packaging an APK: time p4a apk --private ../new-private/ --package=com.aerispos.aeris2 --name="AerisPOS" --version=2.2.19 --bootstrap=sdl2 --requirements=aeris2 --dist_name=aeris2-dist --copy-libs --debug

Previous build time was around 30 minutes (estimated, not measured); with ccache the build time is 6m22s.

ccache stats:

cache hit (direct)                  2046
cache hit (preprocessed)              17
cache miss                             2
called for link                      153
called for preprocessing             183
compile failed                       165
preprocessor error                    78
bad compiler arguments                13
unsupported source language           19
autoconf compile/link                417
no input file                         52
files in cache                      4558
cache size                         145.1 MB
max cache size                       5.0 GB

[akshayaurora]

👍

[inclement]

\o/