build(deps): vendor lpeg

Problem: LPeg is hosted on a single unreliable external hoster, forcing
is to mirror it in neovim/deps, which adds maintenance friction. Also,
we have already vendored the Lua `re.lua` module.

Solution: Vendor all of LPeg v1.1.0; as development is not very active
anymore, this should not add much overhead (and allow us to simplify in
particular the Zig build scripts).

Note: LPeg defines a `luaL_newlib` macro for Lua 5.1, which conflicts
with LuaJIT's extension. This requires inlining the macro defined in
`lptypes.h` and used in `lptree.c`; see README.md for the patch.

src/build_lua.zig

@@ -8,7 +8,6 @@ pub fn build_nlua0(
     optimize: std.builtin.OptimizeMode,
     use_luajit: bool,
     ziglua: *std.Build.Dependency,
-    lpeg: ?*std.Build.Dependency,
     libluv: ?*std.Build.Step.Compile,
     system_integration_options: build.SystemIntegrationOptions,
 ) !*std.Build.Step.Compile {
@@ -60,7 +59,7 @@ pub fn build_nlua0(
 
         mod.addIncludePath(b.path("src"));
         mod.addIncludePath(b.path("src/includes_fixmelater"));
-        try add_lua_modules(b, target.result, mod, lpeg, use_luajit, true, system_integration_options);
+        try add_lua_modules(mod, use_luajit, true);
     }
 
     // for debugging the nlua0 environment
@@ -83,13 +82,9 @@ pub fn build_nlua0(
 }
 
 pub fn add_lua_modules(
-    b: *std.Build,
-    target: std.Target,
     mod: *std.Build.Module,
-    lpeg_dep: ?*std.Build.Dependency,
     use_luajit: bool,
     is_nlua0: bool,
-    system_integration_options: build.SystemIntegrationOptions,
 ) !void {
     const flags = [_][]const u8{
         // Standard version used in Lua Makefile
@@ -97,9 +92,6 @@ pub fn add_lua_modules(
         if (is_nlua0) "-DNVIM_NLUA0" else "",
     };
 
-    if (lpeg_dep) |lpeg| {
-        mod.addIncludePath(lpeg.path(""));
-    }
     mod.addCSourceFiles(.{
         .files = &.{
             "src/mpack/lmpack.c",
@@ -110,25 +102,17 @@ pub fn add_lua_modules(
         },
         .flags = &flags,
     });
-    if (system_integration_options.lpeg) {
-        if (try findLpeg(b, target)) |lpeg_lib| {
-            mod.addLibraryPath(.{ .cwd_relative = std.fs.path.dirname(lpeg_lib).? });
-            mod.addObjectFile(.{ .cwd_relative = lpeg_lib });
-        }
-    } else if (lpeg_dep) |lpeg| {
-        mod.addCSourceFiles(.{
-            .root = .{ .dependency = .{ .dependency = lpeg, .sub_path = "" } },
-            .files = &.{
-                "lpcap.c",
-                "lpcode.c",
-                "lpcset.c",
-                "lpprint.c",
-                "lptree.c",
-                "lpvm.c",
-            },
-            .flags = &flags,
-        });
-    }
+    mod.addCSourceFiles(.{
+        .files = &.{
+            "src/lpeg/lpcap.c",
+            "src/lpeg/lpcode.c",
+            "src/lpeg/lpcset.c",
+            "src/lpeg/lpprint.c",
+            "src/lpeg/lptree.c",
+            "src/lpeg/lpvm.c",
+        },
+        .flags = &flags,
+    });
 
     if (!use_luajit) {
         mod.addCSourceFiles(.{
@@ -184,36 +168,3 @@ pub fn build_libluv(
 
     return lib;
 }
-
-fn findLpeg(b: *std.Build, target: std.Target) !?[]const u8 {
-    const filenames = [_][]const u8{
-        "lpeg_a",
-        "lpeg",
-        "liblpeg_a",
-        "lpeg.so",
-        b.fmt("lpeg{s}", .{target.dynamicLibSuffix()}),
-    };
-    var code: u8 = 0;
-    const dirs_stdout = std.mem.trimEnd(u8, try b.runAllowFail(&[_][]const u8{
-        "pkg-config",
-        "--variable=pc_system_libdirs",
-        "--keep-system-cflags",
-        "pkg-config",
-    }, &code, .ignore), "\r\n");
-    var paths: std.ArrayList([]const u8) = try .initCapacity(b.allocator, 0);
-    var path_it = std.mem.tokenizeAny(u8, dirs_stdout, " ,");
-    while (path_it.next()) |dir| {
-        try paths.append(b.allocator, dir);
-        try paths.append(b.allocator, b.fmt("{s}/lua/5.1", .{dir}));
-    }
-    const io = b.graph.io;
-    for (paths.items) |path| {
-        var dir = std.Io.Dir.openDirAbsolute(io, path, .{}) catch continue;
-        defer dir.close(io);
-        for (filenames) |filename| {
-            dir.access(io, filename, .{}) catch continue;
-            return b.fmt("{s}/{s}", .{ path, filename });
-        }
-    }
-    return null;
-}