make: code refactoring

[gapry]

The following list is the summary of PR

• define the LIBS flags.
• define the variable QEMU and apply it.
• define the variable CROSS_EXEC and apply it
• apply the variable BIN.
• extend the CFLAGS
• define the variable SRC and apply it

[gapry]

@jserv The previous PR has rebased successfully but some commits is lost. Hence, I request again

[jserv]

@gapry : I would like to close the series of changes in favor of incoming "interpreter" and "elf-arm" branch, which require flexible build configurations.

[gapry]

@jserv ok. And I also think the PR is pointless and meaningless. But, thanks for your teaching.