dhcpcd: disable on static library builds

dhcpcd uses dlopen(), so it is not compatible with pure static library
builds.

Fixes:

  http://autobuild.buildroot.net/results/512/51249e8d3487e17bb6a60a99dcbd461f7b591eac/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
gpm: disable on !MMU, requires fork()

Fixes:

  http://autobuild.buildroot.net/results/b2b/b2beb4876fba22f139df9c336ff0fae77354721b/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Merge remote-tracking branch 'mirror/master'