__rebar_compile: Sync FFLAGS, FCFLAGS, and LDFLAGS with %cmake and %configure.

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
__rebar_compile: Compile with -vv to make used command lines visible.

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
__rebar_compile: Rename to rebar_compile for consistency with other such macros.

Also, at least openSUSE has rebar_compile.

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>
__rebar: New macro, use it in rebar_compile.

Signed-off-by: Ville Skyttä <ville.skytta@iki.fi>