rust: Get native-static-libs even when it cannot run host binaries

When rustc cannot run host binaries it does an early return which
skipped getting native-static-libs. Move that code earlier to always run
it.

While at it, failing to determine those libs is a fatal error. We would
crash later when trying to access rustc.native_static_libs attribute
otherwise.

mesonbuild/compilers/rust.py

@@ -84,6 +84,7 @@ class RustCompiler(Compiler):
         pc, stdo, stde = Popen_safe_logged(cmdlist, cwd=work_dir)
         if pc.returncode != 0:
             raise EnvironmentException(f'Rust compiler {self.name_string()} cannot compile programs.')
+        self._native_static_libs(work_dir, source_name)
         if environment.need_exe_wrapper(self.for_machine):
             if not environment.has_exe_wrapper():
                 # Can't check if the binaries run so we have to assume they do
@@ -95,18 +96,22 @@ class RustCompiler(Compiler):
         pe.wait()
         if pe.returncode != 0:
             raise EnvironmentException(f'Executables created by Rust compiler {self.name_string()} are not runnable.')
+
+    def _native_static_libs(self, work_dir: str, source_name: str) -> None:
         # Get libraries needed to link with a Rust staticlib
         cmdlist = self.exelist + ['--crate-type', 'staticlib', '--print', 'native-static-libs', source_name]
         p, stdo, stde = Popen_safe_logged(cmdlist, cwd=work_dir)
-        if p.returncode == 0:
-            match = re.search('native-static-libs: (.*)$', stde, re.MULTILINE)
-            if match:
-                # Exclude some well known libraries that we don't need because they
-                # are always part of C/C++ linkers. Rustc probably should not print
-                # them, pkg-config for example never specify them.
-                # FIXME: https://github.com/rust-lang/rust/issues/55120
-                exclude = {'-lc', '-lgcc_s', '-lkernel32', '-ladvapi32'}
-                self.native_static_libs = [i for i in match.group(1).split() if i not in exclude]
+        if p.returncode != 0:
+            raise EnvironmentException('Rust compiler cannot compile staticlib.')
+        match = re.search('native-static-libs: (.*)$', stde, re.MULTILINE)
+        if not match:
+            raise EnvironmentException('Failed to find native-static-libs in Rust compiler output.')
+        # Exclude some well known libraries that we don't need because they
+        # are always part of C/C++ linkers. Rustc probably should not print
+        # them, pkg-config for example never specify them.
+        # FIXME: https://github.com/rust-lang/rust/issues/55120
+        exclude = {'-lc', '-lgcc_s', '-lkernel32', '-ladvapi32'}
+        self.native_static_libs = [i for i in match.group(1).split() if i not in exclude]
 
     def get_dependency_gen_args(self, outtarget: str, outfile: str) -> T.List[str]:
         return ['--dep-info', outfile]