Adds the ability to build static archives in addition to shared objects

aiter/jit/utils/cpp_extension.py

@@ -1667,6 +1667,7 @@ def sanitize_flags(flags):
     # Version 1.3 is required for the `deps` directive.
     config = ["ninja_required_version = 1.3"]
     config.append(f"cxx = {compiler}")
+    config.append(f"ar = {os.environ.get('AITER_AR_BIN', 'ar')}")
     if with_cuda or cuda_dlink_post_cflags:
         nvcc = _join_rocm_home("bin", "hipcc")
         config.append(f"nvcc = {nvcc}")
@@ -1719,24 +1720,53 @@ def sanitize_flags(flags):
     else:
         devlink_rule, devlink = [], []
 
+    aiter_build_static = os.environ.get("AITER_BUILD_STATIC", "0")
+    emit_static_archive = (
+        library_target is not None and
+        aiter_build_static != "0" and
+        (
+            aiter_build_static in ("1", "all") or
+            os.path.splitext(library_target)[0] in aiter_build_static.split(",")
+        )
+    )
+
     if library_target is not None:
         link_rule = ["rule link"]
 
         link_rule.append(
             "  command = $cxx @$out.rsp $ldflags -o $out\n  rspfile = $out.rsp\n  rspfile_content = $in"
         )
-
         link = [f'build {library_target}: link {" ".join(objects)}']
 
-        default = [f"default {library_target}"]
+        if emit_static_archive:
+            archive_rule = ["rule archive"]
+            archive_rule.append(
+                "  command = rm -f $out && $ar rcs $out @$out.rsp\n  rspfile = $out.rsp\n  rspfile_content = $in"
+            )
+
+            archive_target = os.path.splitext(library_target)[0] + ".a"
+            archive = [f'build {archive_target}: archive {" ".join(objects)}']
+            default = [f"default {library_target} {archive_target}"]
+        else:
+            archive_rule, archive = [], []
+            default = [f"default {library_target}"]
     else:
-        link_rule, link, default = [], [], []
+        link_rule, archive_rule, link, archive, default = [], [], [], [], []
 
     # 'Blocks' should be separated by newlines, for visual benefit.
     blocks = [config, flags, compile_rule]
     if with_cuda:
         blocks.append(cuda_compile_rule)  # type: ignore[possibly-undefined]
-    blocks += [devlink_rule, link_rule, build, devlink, link, default]
+    blocks += [
+        devlink_rule,
+        link_rule,
+        archive_rule,
+        build,
+        devlink,
+        link,
+        archive,
+        default,
+    ]
     content = "\n\n".join("\n".join(b) for b in blocks)
     # Ninja requires a new lines at the end of the .ninja file
     content += "\n"