[gcc r14-7987] gccrs: Supress error with proc macro crates

[Arthur Cohen]

https://gcc.gnu.org/g:ccef457297594c5eadf57ec402122f260c1edc8f

commit r14-7987-gccef457297594c5eadf57ec402122f260c1edc8f
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Tue Aug 1 18:32:46 2023 +0200

    gccrs: Supress error with proc macro crates
    
    This error was emitted when a valid proc macro crate was loaded. Proc
    macros do not contain any import data for now.
    
    gcc/rust/ChangeLog:
    
            * metadata/rust-imports.cc (Import::try_package_in_directory):
            Remove error when some macro are found even if no import data is
            available.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 gcc/rust/metadata/rust-imports.cc | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/gcc/rust/metadata/rust-imports.cc b/gcc/rust/metadata/rust-imports.cc
index fc6bcdb2d95..17451fbcb9b 100644
--- a/gcc/rust/metadata/rust-imports.cc
+++ b/gcc/rust/metadata/rust-imports.cc
@@ -174,9 +174,10 @@ Import::try_package_in_directory (const std::string &filename,
 
   close (fd);
 
-  rust_error_at (location,
-		 "%s exists but does not contain any Rust export data",
-		 found_filename.c_str ());
+  if (macros.empty ())
+    rust_error_at (location,
+		   "%s exists but does not contain any Rust export data",
+		   found_filename.c_str ());
 
   return std::make_pair (NULL, macros);
 }