Add .gn files

.gn

@@ -0,0 +1,11 @@
+# This file is used by the GN meta build system to find the root of the source
+# tree and to set startup options. For documentation on the values set in this
+# file, run "gn help dotfile" at the command line.
+
+buildconfig = "//build/config/BUILDCONFIG.gn"
+
+check_targets = [
+    "//libraries/*",
+    "//plugins/*",
+    "//programs/*"
+]

BUILD.gn

@@ -0,0 +1,18 @@
+flags = []
+if(build_type == "debug") {
+    flags += ["-O0", "-g"]
+}
+else if(build_type == "release") {
+    flags += ["-O3", "-DNDEBUG"]
+}
+
+config("root") {
+    cflags_cc = [
+        "-std=c++17",
+        "-Wall",
+        "-Wextra",
+        "-Werror",
+        "-Wno-unused-parameter"
+    ] + flags
+}
+