By setting RUSTFLAGS in the Cargo config we run into the situation that
when doing a host build, all rust files are compiled with the flags,
including build.rs. When cross-compiling, build.rs is not build with the
RUSTFLAGS specified. That makes kind of sense, but it also means that
all the build scripts are always recompiled when switching between a
target and a host build - and that applies to *all* packages, including
dependencies.
So short of a better solution, this patch removes the need to set
RUSTFLAGS. It was used to extract the system library dependencies for
the static library we'd create. Instead we're now building two shared
libraries and are linking against them. They contain the rust library
twice, so that's not really a desirable final state either, but
productivity wins right now :-)
It might make sense to go back to creating *one* shared library through
a dedicated crate and -- since 'pub extern "C"' functions are not
transitively exported, it may require re-exporting them by hand or using
some clever build trick perhaps.
* Fix text-file-busy error when running the binary by replacing the use
of named temp file with simply using the input source file and the
extension replaced. A scope guard make sure to also delete the binary.
* Fix hard-coded library dependencies by sharing code with the cmake
xtask that needs the same list.
Don't try to determine the native libs dependency *and* the artifact
collection in one go by setting RUSTFLAGS, as that causes everything to
be rebuilt over and over again.
Instead, go back to invoking rustc once to determine the native libs
dependencies.
Call cargo only once by building the target package (gl renderer) right
away and passing the RUSTFLAGS to get the native library dependency.
Suggested by Olivier :)
This is done by calling cargo with json output to build the libraries,
collect the .a files, extract the native libraries needed for final
linkage and pass all that to a CMake project that cobbles together the
.a files into a propery cmake target with include paths, etc.
