all: move standalone libraries to libs/ subdirectory

The root dir of our repository has grown quite a lot the past few months.

I'd like to make it more clear where the bulk of the engine lives (`src/`) and
also make it more clear which Mach libraries are consumable as standalone projects.

As for the name of this directory, `libs` was my first choice but there's a bit of
a convention of that being external libraries in Zig projects _today_, while these
are libraries maintained as part of Mach in this repository - not external ones.

We will name this directory `libs`, and if we have a need for external libraries
we will use `external` or `deps` for that directory name. I considered other names
such as `components`, `systems`, `modules` (which are bad as they overlap with
major ECS / engine concepts), and it seems likely the official Zig package manager
will break the convention of using a `libs` dir anyway.

Performed via:

```sh
mkdir libs/
git mv freetype libs/
git mv basisu libs/
git mv gamemode libs/
git mv glfw libs/
git mv gpu libs/
git mv gpu-dawn libs/
git mv sysaudio libs/
git mv sysjs libs/
git mv ecs libs/
```

git-subtree-dir: glfw
git-subtree-mainline: 0d5b853443
git-subtree-split: 572d1144f11b353abdb64fff828b25a4f0fbb7ca

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

git mv ecs libs/

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

libs/gpu-dawn/src/dawn/mingw_helpers.cpp

@@ -0,0 +1,56 @@
+#ifdef __MINGW32__
+#include <guiddef.h>
+#include <stdint.h>
+
+#define MINGW_UUIDOF(type, spec)                                              \
+    extern "C++" {                                                            \
+    struct __declspec(uuid(spec)) type;                                       \
+    template<> const GUID &__mingw_uuidof<type>() {                           \
+        static constexpr IID __uuid_inst = guid_from_string(spec);            \
+        return __uuid_inst;                                                   \
+    }                                                                         \
+    template<> const GUID &__mingw_uuidof<type*>() {                          \
+        return __mingw_uuidof<type>();                                        \
+    }                                                                         \
+    }
+
+constexpr uint8_t nybble_from_hex(char c) {
+  return ((c >= '0' && c <= '9')
+              ? (c - '0')
+              : ((c >= 'a' && c <= 'f')
+                     ? (c - 'a' + 10)
+                     : ((c >= 'A' && c <= 'F') ? (c - 'A' + 10)
+                                               : /* Should be an error */ -1)));
+}
+
+constexpr uint8_t byte_from_hex(char c1, char c2) {
+  return nybble_from_hex(c1) << 4 | nybble_from_hex(c2);
+}
+
+constexpr uint8_t byte_from_hexstr(const char str[2]) {
+  return nybble_from_hex(str[0]) << 4 | nybble_from_hex(str[1]);
+}
+
+constexpr GUID guid_from_string(const char str[37]) {
+  return GUID{static_cast<uint32_t>(byte_from_hexstr(str)) << 24 |
+                  static_cast<uint32_t>(byte_from_hexstr(str + 2)) << 16 |
+                  static_cast<uint32_t>(byte_from_hexstr(str + 4)) << 8 |
+                  byte_from_hexstr(str + 6),
+              static_cast<uint16_t>(
+                  static_cast<uint16_t>(byte_from_hexstr(str + 9)) << 8 |
+                  byte_from_hexstr(str + 11)),
+              static_cast<uint16_t>(
+                  static_cast<uint16_t>(byte_from_hexstr(str + 14)) << 8 |
+                  byte_from_hexstr(str + 16)),
+              {byte_from_hexstr(str + 19), byte_from_hexstr(str + 21),
+               byte_from_hexstr(str + 24), byte_from_hexstr(str + 26),
+               byte_from_hexstr(str + 28), byte_from_hexstr(str + 30),
+               byte_from_hexstr(str + 32), byte_from_hexstr(str + 34)}};
+}
+
+#endif // __MINGW32__
+
+// The point of this helper file is to export the specializations for MINGW_UUIDOF
+// below, since MinGW does not have these as part of dxguid yet (not completely up
+// to date.)
+MINGW_UUIDOF(IDXGraphicsAnalysis, "9f251514-9d4d-4902-9d60-18988ab7d4b5")

libs/gpu-dawn/src/main.zig

@@ -0,0 +1 @@
+pub fn main() void {}