The -Qunused-arguments flag disables the warning where some flags are
not relevant to a compilation. This commonly happens when compiling
assembly files (.s or .S files) because some flags are specific to C and
not relevant to assembly.
Because practically all baremetal targets need some form of assembly,
this flag is added to most CFlags. This creates a lot of noise. And it
is also added for compiling C code where it might hide bugs (by hiding
the fact a flag is actually unused).
This commit adds the flag to all assembly compilations and removes them
from all target JSON files.
Setting the linker script as one property (instead of as part of the
generic ldflags property) allows it to be overriden.
This is important for the SoftDevice on Nordic chips, because the
SoftDevice takes up a fixed part of the flash/RAM and the application
must be flashed at a different position. With this linkerscript option,
it is possible to create (for example) a pca10040-s132v6 that overrides
the default linker script.
