aom: use `ENV.runtime_cpu_detection`

Also, remove the revision bump, make the changes from #85801 conditional
on macOS, and clean up the style a little.

Formula/aom.rb

@@ -5,7 +5,6 @@ class Aom < Formula
       tag:      "v3.2.0",
       revision: "287164de79516c25c8c84fd544f67752c170082a"
   license "BSD-2-Clause"
-  revision 1
 
   bottle do
     sha256 cellar: :any,                 arm64_big_sur: "6e289d13b26ea36b824c282e2dda13182d044769e5de4808cc6b400f82893f3e"
@@ -16,10 +15,14 @@ class Aom < Formula
   end
 
   depends_on "cmake" => :build
-  depends_on "pkg-config" => :build
   depends_on "yasm" => :build
+
+  # `jpeg-xl` is currently not bottled on Linux
+  on_macos do
+    depends_on "pkg-config" => :build
     depends_on "jpeg-xl"
     depends_on "libvmaf"
+  end
 
   resource "bus_qcif_15fps.y4m" do
     url "https://media.xiph.org/video/derf/y4m/bus_qcif_15fps.y4m"
@@ -27,10 +30,9 @@ class Aom < Formula
   end
 
   def install
-    mkdir "macbuild" do
+    ENV.runtime_cpu_detection unless Hardware::CPU.arm?
+
     args = std_cmake_args.concat(["-DCMAKE_INSTALL_RPATH=#{rpath}",
-                                    "-DCONFIG_TUNE_BUTTERAUGLI=1",
-                                    "-DCONFIG_TUNE_VMAF=1",
                                   "-DENABLE_DOCS=off",
                                   "-DENABLE_EXAMPLES=on",
                                   "-DENABLE_TESTDATA=off",
@@ -39,10 +41,18 @@ class Aom < Formula
                                   "-DBUILD_SHARED_LIBS=on"])
     # Runtime CPU detection is not currently enabled for ARM on macOS.
     args << "-DCONFIG_RUNTIME_CPU_DETECT=0" if Hardware::CPU.arm?
-      system "cmake", "..", *args
 
-      system "make", "install"
+    # Make unconditional when `jpeg-xl` is bottled on Linux
+    if OS.mac?
+      args += [
+        "-DCONFIG_TUNE_BUTTERAUGLI=1",
+        "-DCONFIG_RUNTIME_CPU_DETECT=1",
+      ]
     end
+
+    system "cmake", "-S", ".", "-B", "brewbuild", *args
+    system "cmake", "--build", "brewbuild"
+    system "cmake", "--install", "brewbuild"
   end
 
   test do

style_exceptions/runtime_cpu_detection_allowlist.json

@@ -1,4 +1,5 @@
 [
+  "aom",
   "apache-arrow",
   "fftw",
   "libvpx",