Configure compilation options and compiler autoconf - makefile

Question

I'm working on a personal project with Rust and tcl but i still want to use the classic makefile structure.
I know that to compile multifile I just need to declare mod second on main.rs and rustc automatically connect the modules. So I use
$ rustc main.rs -o output -C debuginfo=2
Now I tried to integrate autoconf and automake because I want to make a configure script to check for tcl, rustup etc... But I don't know how to edit to compile with rustc and its options insead of cc and c options (like trying a .o that doesn't compile because they don't have a main function).
for the configure.ac i used:
AC_CONFIG_SRCDIR([source/main.rs])
AC_CONFIG_AUX_DIR(config)
# I manually checked for rustup and tclsh
AM_INIT_AUTOMAKE
AC_CONFIG_FILES([Makefile])
AC_OUTPUT
for the Makefile.am:
AUTOMAKE_OPTIONS = foreign
bin_PROGRAMS = output
SUBDIRS = sources
output_SOURCES = sources/main.rs
I have the main directory with configure.ac and Makefile.am and the sources directory with all the stuff (and also the config directory for autoconf)

Answer 1

Now I tried to integrate autoconf and automake because I want to make a configure script to check for tcl, rustup etc...
The configure script is the responsibility of Autoconf. It is not obligatory to use Automake together with Autoconf, and you should consider whether it would be sensible for you to use Autoconf alone. That would give you complete control over the generated Makefile, as you would write a Makefile.in directly instead of relying on Automake to do that for you. Presumably, you would write a much simpler Makefile.in than Automake generates, and that's fine.
Automake is not necessarily out of the question, but its manual has this to say about language support:
Automake currently only includes full support for C, C++ (see C++
Support), Objective C (see Objective C Support), Objective C++ (see
Objective C++ Support), Fortran 77 (see Fortran 77 Support), Fortran
9x (see Fortran 9x Support), and Java (see Java Support with gcj).
There is only rudimentary support for other languages, support for
which will be improved based on user demand.
Some limited support for adding your own languages is available via
the suffix rule handling (see Suffixes).
The referenced section about suffix rules shows how you might use such a rule to teach Automake how to build Rust programs. It might look something like this:
.rs:
$(RUSTC) $< -o $# $(AM_RUSTFLAGS) $(RUSTFLAGS)
SUFFIXES = .rs
That assumes that configure will identify the Rust compiler and export its name as RUSTC. AM_RUSTFLAGS is for defining compilation flags internally in your project (typically in your Makefile.am), and RUSTFLAGS is for the builder to add or override compilation flags at build time.
But since the compiler does not produce intermediate object files (or so I gather), I would expect that defining sources in output_SOURCES would not yield a working Makefile, and that you would probably need the name of the top-level Rust source to match the name of the wanted binary (i.e. output.rs instead of main.rs). The single-suffix rule should, then, get your binary built without any sources being explicitly specified. You would also want to name all contributing Rust sources in the EXTRA_SOURCES variable, else they would be omitted from distribution packages built via make dist.
Note, too, that the above does not define all the build dependencies that actually exist if you're building multifile programs. I would suggest doing that by adding an appropriate prerequisite-only rule, such as
output: $(output_extra_sources)
(with no recipe) in multifile cases. This will ensure that make will recognize when output needs to be rebuilt as a result of a modification to one of its sources other than output.rs.