Fix Linux buildCabbage script
Fix echo of MakefilePluginEffect and MakefilePluginSynth

Fix echo for linking, clean and strip of MakefilePluginEffect and
MakefilePluginSynth.
Delete apparently useless Makefile (for Linux build)
Refix Linux buildCabbage (no need for more than one cleaning)

Only MakefileStandalone clean is required, the
others (MakefilePlugin{Effect,Synth} clean) are merely doing the same
thing, which is actually detrimental.

Also pass the arguments of buildCabbage to MakefileStandalone clean,
that way OBJDIR is defined correctly (depending on CONFIG).
Echo compiler commands (useful for debugging)

We may want to wrap that into a conditional with some Make variable
VERBOSE in case this doesn't make everyone happy.
Delete all Linux build files from the working tree

Build files have not their place in the source code. It confuses the
developer as git keeps track of them, IMO. It also makes the source
code larger and the time to send/receive the commits over the network
longer.
Remove useless extra -I in the compiling option

Nothing harmless except that extra -I would generate a warning.
Re-add MakefilePluginEffect clean and MakefilePluginSynth clean

As it seems, those builds are actually independent!
Add VERBOSE variable in makefiles to echo compiling commands

Set VERBOSE to yes if you want to echo compiling commands.
Merge pull request #10 from ngeiswei/fix_linux_build

Fix linux build