Normally when the language modules are built, they are built directly
into the build/lib/unit/modules/ directory.

This then allows Unit to find them without being installed. This is
useful for things like the pytests.

This wasn't happening for the wasm-wasi-component language module. So we
now copy it over and give it the right name as part of the make/build
process.

Reported-by: Andrei Zeliankou <zelenkov@nginx.com>
Fixes: 4e6d7e876 ("Wasm-wc: Wire it up to the build system")
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Have cargo run if for example src/wasm-wasi-component/src/lib.rs is
changed, or any of the other files that should perhaps trigger a
rebuild.

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

-o is not available on macOS 12.7 at least, and it's what homebrew seems
to support still.

Also, the proposed switch seems to be used already in the codebase.

cargo build creates the language module under
src/wasm-wasi-component/target/release/libwasm_wasi_component.so and not
build/lib/unit/modules/wasm_wasi_component.unit.so which is what we were
using as a target dependency in the Makefile which doesn't exist so this
resulted in the following

  $ make wasm-wasi-component-install
  cargo build --release --manifest-path src/wasm-wasi-component/Cargo.toml
      Finished release [optimized] target(s) in 0.17s
  install -d /opt/unit/modules
  install -p src/wasm-wasi-component/target/release/libwasm_wasi_component.so \
          /opt/unit/modules/wasm_wasi_component.unit.so

I.e it wanted to rebuild the module, after this patch we get the more
correct

  $ make wasm-wasi-component-install
  install -d /opt/unit/modules
  install -p src/wasm-wasi-component/target/release/libwasm_wasi_component.so \
          /opt/unit/modules/wasm_wasi_component.unit.so

This is all a little ugly because we're fighting against cargo wanting
to do its own thing and this wasm-wasi-component language module build
process is likely going to get some re-working anyway, so this will do
for now.

Reported-by: Konstantin Pavlov <thresh@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Rather than calling make itself to build nxt_unit.o make nxt_unit.o a
dependency of the main module build target.

Reported-by: Konstantin Pavlov <thresh@nginx.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Et voila...

  $ ./configure wasm-wasi-component
  configuring wasm-wasi-component module
  Looking for rust compiler ... found.
  Looking for cargo ... found.
   + wasm-wasi-component module: wasm_wasi_component.unit.so
  $ make install
  test -d /opt/unit/sbin          || install -d /opt/unit/sbin
  install -p build/sbin/unitd /opt/unit/sbin/
  test -d /opt/unit/state                 || install -d /opt/unit/state
  test -d /opt/unit               || install -d /opt/unit
  test -d /opt/unit               || install -d /opt/unit
  test -d /opt/unit/share/man/man8                || install -d /opt/unit/sh
man/man8
  install -p -m644 build/share/man/man8/unitd.8           /opt/unit/share/ma
n8/
  make build/src/nxt_unit.o
  make[1]: Entering directory '/home/andrew/src/unit'
  make[1]: 'build/src/nxt_unit.o' is up to date.
  make[1]: Leaving directory '/home/andrew/src/unit'
  cargo build --release --manifest-path src/wasm-wasi-component/Cargo.toml
      Finished release [optimized] target(s) in 0.55s
  install -d /opt/unit/modules
  install -p src/wasm-wasi-component/target/release/libwasm_wasi_component.so \
          /opt/unit/modules/wasm_wasi_component.unit.so

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>