A few words on sofort's tool-finding logic

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# the goals of sofort's tool-finding logic are:

- follow a clear, transparent, and consistent logic

- allow users to easily specify per-build preferences

- allow distros to easily and cleanly use site-wide settings

# three-way terminology:

- native machine: where make(1) will be running.

- host machine:   where the package's program or libraries will execute.

- target machine: where code generated by the host package will execute.

! NOTE, however, that the host/target distinction is only relevant

  when building a code-generating utility (e.g. a compiler), and that

  the two are otherwise rather synonymous. Moreover, in practice it

  is much more common to see configure scripts being invoked with a

  --target=<machine> argument specifying the host, than with a

  --host=<machine> argument.

# invocation and names of binary tools:

- agnostic names (ar, nm, objdump, ...)

- branded names (llvm-ar, llvm-nm, llvm-objdump, ...)

- machine-prefixed agnostic names (x86_64-nt64-midipix-ar, ...)

- machine-prefixed branded names (x86_64-linux-gnu-gcc-ar, ...)

- machine-specifying branded tools, as in

  llvm-ar --target=x86_64-linux.

# cross-compilation: default search order:

- machine-prefixed agnostic tools

- machine-prefixed branded tools, starting with the prefix

  most commonly associated with the selected compiler (that is,

  ``gcc'' when using gcc, and ``llvm'' when using clang)

- (machine-specifying) agnostic tools

- (machine-speficying) branded tools, starting once again with the

  prefix most commonly associated with the selected compiler

# native builds: default search order:

- agnostic tools

- machine-prefixed agnostic tools

- machine-prefixed branded tools

- branded tools

# using an alternate search order:

- --toolchain=<prefix> (e.g. --toolchain=llvm) --> search for tools

  that begin with <prefix> before searching for agnostic tools

# restricting which tools may be searched:

- --zealous          --> only search for agnostic tools

- --zealous=<prefix> --> only search for <prefix>-branded tools

# per-tool overrides, by example of the ``ar'' tool:

- AR=ar          --> set AR to $(command -v ar)

- AR=/path/to/ar --> set AR to the specified absolute path

# host generated config file and variable names:

- ccenv/host.mk

- AR, NM, OBJDUMP, ...

# native generated config file and variable names:

- ccenv/native.mk

- NATIVE_AR, NATIVE_NM, NATIVE_OBJDUMP, ...

# distro: site-wide preferences

- --ccenv=/path/to/site-specific/ccenv

- use the above to create ccenv as a symlink to

  /path/to/site-specific/ccenv, and to accordingly

  skip configure's tool-finding step.