Meta: Add serenity toolchain to gn build

Meta/gn/build/BUILD.gn

@@ -142,6 +142,7 @@ config("compiler_defaults") {
   if (sysroot != "") {
     if (current_os != "mac" && current_os != "android") {
       cflags += [ "--sysroot=" + rebase_path(sysroot, root_build_dir) ]
+      ldflags += [ "--sysroot=" + rebase_path(sysroot, root_build_dir) ]
     }
   }
 

Meta/gn/build/serenity_target.gni

@@ -0,0 +1,31 @@
+declare_args() {
+  # Serenity architecture to build for
+  serenity_arch = "x86_64"
+
+  # Serenity compiler to use, Clang or GNU
+  serenity_toolchain = "GNU"
+}
+
+if (serenity_toolchain == "GNU") {
+  toolchain_root =
+      rebase_path("//Toolchain/Local/$serenity_arch/", root_build_dir)
+  toolchain_bin = toolchain_root + "bin/"
+
+  serenity_cc = toolchain_bin + serenity_arch + "-pc-serenity-gcc"
+  serenity_cxx = toolchain_bin + serenity_arch + "-pc-serenity-g++"
+  serenity_ld = serenity_cxx
+  serenity_nm = toolchain_bin + serenity_arch + "-pc-serenity-nm"
+  serenity_objcopy = toolchain_bin + serenity_arch + "-pc-serenity-objcopy"
+  serenity_compiler_version = "13.1.0"
+} else {
+  assert(serenity_toolchain == "Clang",
+         "Expected GNU or Clang for serenity_toolchain")
+  toolchain_root = rebase_path("//Toolchain/Local/clang/", root_build_dir)
+  toolchain_bin = toolchain_root + "bin/"
+  serenity_cc = toolchain_bin + serenity_arch + "-pc-serenity-clang"
+  serenity_cxx = toolchain_bin + serenity_arch + "-pc-serenity-clang++"
+  serenity_ld = serenity_cxx
+  serenity_nm = toolchain_bin + "llvm-nm"
+  serenity_objcopy = toolchain_bin + "llvm-objcopy"
+  serenity_compiler_version = "16"
+}

Meta/gn/build/sysroot.gni

@@ -1,4 +1,7 @@
 declare_args() {
   # Path of sysroot to use.
   sysroot = ""
+  if (current_os == "serenity") {
+    sysroot = "$root_build_dir/Root"
+  }
 }

Meta/gn/build/toolchain/BUILD.gn

@@ -1,3 +1,6 @@
+import("//Meta/gn/build/serenity_target.gni")
+import("//Meta/gn/build/toolchain/compiler.gni")
+
 unix_copy_command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
 
 template("unix_toolchain") {
@@ -10,6 +13,13 @@ template("unix_toolchain") {
     forward_variables_from(invoker.toolchain_args, "*")
     forward_variables_from(invoker, "*")
 
+    not_needed([
+                 "current_cpu",
+                 "cc",
+                 "is_clang",
+                 "use_lld",
+               ])
+
     tool("cc") {
       depfile = "{{output}}.d"
       command = "$cc -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}}"
@@ -55,11 +65,13 @@ template("unix_toolchain") {
       description = "AR {{output}}"
       outputs = [ "{{output_dir}}/{{target_output_name}}.a" ]
       output_prefix = "lib"
-      if (current_os != "serenity") {
+      if (current_os == "serenity") {
+        default_output_dir = "{{target_out_dir}}"
+      } else {
         output_prefix = "liblagom-"
-      }
         default_output_dir = "{{root_out_dir}}/lib"
       }
+    }
 
     # Make these apply to all tools below.
     lib_switch = "-l"
@@ -77,11 +89,13 @@ template("unix_toolchain") {
       description = "SOLINK $outfile"
       outputs = [ outfile ]
       output_prefix = "lib"
-      if (current_os != "serenity") {
+      if (current_os == "serenity") {
+        default_output_dir = "{{target_out_dir}}"
+      } else {
         output_prefix = "liblagom-"
-      }
         default_output_dir = "{{root_out_dir}}/lib"
       }
+    }
 
     tool("solink_module") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
@@ -94,11 +108,13 @@ template("unix_toolchain") {
       }
       description = "SOLINK $outfile"
       outputs = [ outfile ]
-      if (current_os != "serenity") {
+      if (current_os == "serenity") {
+        default_output_dir = "{{target_out_dir}}"
+      } else {
         output_prefix = "lagom-"
-      }
         default_output_dir = "{{root_out_dir}}/lib"
       }
+    }
 
     tool("link") {
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
@@ -110,10 +126,14 @@ template("unix_toolchain") {
       description = "LINK $outfile"
       outputs = [ outfile ]
 
+      if (current_os == "serenity") {
         # Setting this allows targets to override the default executable output by
         # setting output_dir.
+        default_output_dir = "{{target_out_dir}}"
+      } else {
         default_output_dir = "{{root_out_dir}}/bin"
       }
+    }
 
     tool("copy") {
       command = unix_copy_command
@@ -157,4 +177,15 @@ unix_toolchain("unix") {
     cxx = host_cxx
   }
 }
-# Note: For serenity, we can override cc and cxx etc in toolchain_args
+
+unix_toolchain("serenity") {
+  cc = serenity_cc
+  cxx = serenity_cxx
+  ld = serenity_ld
+  toolchain_args = {
+    current_os = "serenity"
+    current_cpu = serenity_arch
+    is_clang = serenity_toolchain == "Clang"
+    use_lld = is_clang
+  }
+}

Meta/gn/build/toolchain/compiler.gni

@@ -1,6 +1,6 @@
 declare_args() {
   # Set to true when host compiler is clang so that clang flags will be passed to it
-  is_clang = host_os == "mac"
+  is_clang = current_os == "mac"
 
   # Enable setting -fuse-ld and other flags for using the lld linker.
   # Should not be set on macOS when using the default system compiler.