[PATCH v3 0/9] build improvements

[Johannes Berg]

Here's a fixed up version of the patchset, with the following changes:
 * fix .d file generation, CFLAGS were messed up due to .config file
   handling, moved that inside the common build system which simplifies
   things anyway
 * remove hostapd vs. wpa_s driver build checks - that was evidently
   trying to do some cleanups to achieve building without "make clean"
   but not nearly sufficient, and this patchset addresses the issue
 * make files depend on the .config file so they get rebuilt if the
   configuration changes

johannes