Include linker flags for package note in %build_rustflags

%build_rustflags was used in %cargo_prep, which is executed in %prep,
when %buildsubdir is not set yet. To avoid this, insertion of flags is
moved to an environment variable that is set for %cargo_build and
%cargo_test.

The linker flag gets passed to rustc, and resulting binaries seem to have
note as expected.

data/macros.cargo

@@ -4,7 +4,7 @@
 # it never writes to ~/.cargo during rpmbuild.
 # We also need RUSTC_BOOTSTRAP since we use -Z avoid-dev-deps
 # until it gets stabilized: https://github.com/rust-lang/cargo/issues/5133
-%__cargo %{_bindir}/env CARGO_HOME=.cargo RUSTC_BOOTSTRAP=1 %{_bindir}/cargo
+%__cargo %{_bindir}/env CARGO_HOME=.cargo RUSTC_BOOTSTRAP=1 RUSTFLAGS='%{build_rustflags}' %{_bindir}/cargo
 %__cargo_common_opts %{?_smp_mflags} -Z avoid-dev-deps
 %__cargo_inspector %{_bindir}/cargo-inspector
 
@@ -20,7 +20,6 @@ cat > .cargo/config << EOF \
 [build]\
 rustc = "%{__rustc}"\
 rustdoc = "%{__rustdoc}"\
-rustflags = %{__global_rustflags_toml}\
 \
 [env]\
 CFLAGS = "%{build_cflags}"\

data/macros.rust

@@ -5,7 +5,9 @@
 %build_rustflags %{shrink:
   -Copt-level=3
   -Cdebuginfo=2
-  -Clink-arg=-Wl,-z,relro,-z,now
+  -Clink-arg=-Wl,-z,relro
+  -Clink-arg=-Wl,-z,now
+  %{?_package_note_file:-Clink-arg=-Wl,-dT,%{_package_note_file}}
   -Ccodegen-units=1
   --cap-lints=warn
 }