option to choose your local apps_bin path

[dengzq1234]

The origin experimental --tools-dir is functional when "ete3 build -w .....", but it doesn't work to subcommand such as "check". Changes that I made:

1. read the arguments before load the apps_bin;
2. muted the "require=True" in workflow argument, ortherwise it goes error

example:
ete3 build check -L [custom path], TOOLCHAIN, LOCAL

I wonder if there is more elegant way?

[dengzq1234]

there are conficts with the main branch with big change. Consider discussion and temporary use --tools-dir as experimental solution