Drop MacOS paths

We won't build on Macs.

Change-Id: I6ae8e8fdac379a4acd5335312f20dc4c5cd16254
Remove unneeded commented out linking of libdb

Change-Id: Iccb0c2a41358dbc6ee9ede61d6752623f498227b
Drop unneeded dependencies from rules

Change-Id: I2f955bb1e45d65127fdc3bcbe78a8638207f6d49
Use GNU Make's implicit rules to build object and executable files

Thereby, CFLAGS, LDFLAGS and all the other environment variables get
actually used.

We drop -g from default CFLAGS, as debugging information are not
needed in a release.

Change-Id: I9409458ee75872fb6eb884ed866c7b2c5a122050
Provide definitions to system level functions

Hence, -Wall will complain less

Change-Id: I315417b381e83654b2f9e2a75f55e1b5605065f1
Remove unused variables

Change-Id: Ib19cef3e3730c0c4e3a784e79d2f80e0057d29ef
Provide definition of setgroups function

Change-Id: I9ea973583277035cd1d8b4f836dae81efaeb2188