libstore-tests: Split bench-main into a separate file

This makes it easier to add new benchmarks.

src/libstore-tests/bench-main.cc

@@ -0,0 +1,14 @@
+#include <benchmark/benchmark.h>
+#include "nix/store/globals.hh"
+
+// Custom main to initialize Nix before running benchmarks
+int main(int argc, char ** argv)
+{
+    // Initialize libstore
+    nix::initLibStore(false);
+
+    // Initialize and run benchmarks
+    ::benchmark::Initialize(&argc, argv);
+    ::benchmark::RunSpecifiedBenchmarks();
+    return 0;
+}

src/libstore-tests/derivation-parser-bench.cc

@@ -3,7 +3,6 @@
 #include "nix/store/store-api.hh"
 #include "nix/util/experimental-features.hh"
 #include "nix/store/store-open.hh"
-#include "nix/store/globals.hh"
 #include <fstream>
 #include <sstream>
 
@@ -31,15 +30,3 @@ static void BM_ParseRealDerivationFile(benchmark::State & state, const std::stri
 // Register benchmarks for actual test derivation files if they exist
 BENCHMARK_CAPTURE(BM_ParseRealDerivationFile, hello, std::string(NIX_UNIT_TEST_DATA) + "/derivation/hello.drv");
 BENCHMARK_CAPTURE(BM_ParseRealDerivationFile, firefox, std::string(NIX_UNIT_TEST_DATA) + "/derivation/firefox.drv");
-
-// Custom main to initialize Nix before running benchmarks
-int main(int argc, char ** argv)
-{
-    // Initialize libstore
-    nix::initLibStore(false);
-
-    // Initialize and run benchmarks
-    ::benchmark::Initialize(&argc, argv);
-    ::benchmark::RunSpecifiedBenchmarks();
-    return 0;
-}

src/libstore-tests/meson.build

@@ -110,9 +110,14 @@ test(
 if get_option('benchmarks')
   gbenchmark = dependency('benchmark', required : true)
 
+  benchmark_sources = files(
+    'bench-main.cc',
+    'derivation-parser-bench.cc',
+  )
+
   benchmark_exe = executable(
     'nix-store-benchmarks',
-    'derivation-parser-bench.cc',
+    benchmark_sources,
     config_priv_h,
     dependencies : deps_private_subproject + deps_private + deps_other + [gbenchmark],
     include_directories : include_dirs,