dependencies/boost.py: ignore unknown files

If we encounter a file under the Boost library directory that doesn't
look like a Boost library binary, we should ignore it.

We log a warning for each file we ignore, except for ones we know are
safe to ignore (e. g. PDB files from the SourceForge Windows
distribution).  This should avoid polluting the log.

Fixes #8325.

mesonbuild/dependencies/boost.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import re
+import dataclasses
 import functools
 import typing as T
 from pathlib import Path
@@ -83,6 +84,10 @@ if T.TYPE_CHECKING:
 #     2.4 Ensure that all libraries have the same boost tag (and are thus compatible)
 #   3. Select the libraries matching the requested modules
 
+@dataclasses.dataclass(eq=False, order=False)
+class UnknownFileException(Exception):
+    path: Path
+
 @functools.total_ordering
 class BoostIncludeDir():
     def __init__(self, path: Path, version_int: int):
@@ -152,7 +157,7 @@ class BoostLibraryFile():
         elif self.nvsuffix in ['a', 'lib']:
             self.static = True
         else:
-            raise DependencyException(f'Unable to process library extension "{self.nvsuffix}" ({self.path})')
+            raise UnknownFileException(self.path)
 
         # boost_.lib is the dll import library
         if self.basename.startswith('boost_') and self.nvsuffix == 'lib':
@@ -623,8 +628,15 @@ class BoostDependency(SystemDependency):
                 continue
             if not any([i.name.startswith(x) for x in ['libboost_', 'boost_']]):
                 continue
+            # Windows binaries from SourceForge ship with PDB files alongside
+            # DLLs (#8325).  Ignore them.
+            if i.name.endswith('.pdb'):
+                continue
 
+            try:
                 libs.add(BoostLibraryFile(i.resolve()))
+            except UnknownFileException as e:
+                mlog.warning('Boost: ignoring unknown file {} under lib directory'.format(e.path.name))
 
         return [x for x in libs if x.is_boost()]  # Filter out no boost libraries