exclude more files and remove main in test.cc

Author: HannahShiSFB

Package.swift

@@ -56,6 +56,9 @@ let package = Package(
         "absl/base/internal/spinlock_linux.inc",
         "absl/base/internal/spinlock_posix.inc",
         "absl/base/internal/spinlock_win32.inc",
+        // other files
+        "absl/flags/flag_benchmark.lds",
+        "absl/abseil.podspec.gen.py",
       ],
       sources: [
         "absl/"

SwiftPMTests/build-test/test.cc

@@ -48,4 +48,5 @@
 #include "absl/types/variant.h"
 
 // Test for duplicate `_main` symbol.
-int main(int argc, char** argv) {}
+// _main is defined in runner.swift, any other definition of `_main` in abseil
+// files will cause a duplicate symbol error.