Move optimization flag selection out of cc wrapper

The mapping of architectures to optimization flags is now retrieved from
Hardware::CPU and the selected flags are passed as an environmen
variable, rather than duplicated in the cc wrapper and re-calculated on
every invocation of the compiler.

Closes Homebrew/homebrew#24540.

Library/ENV/4.3/cc

@@ -184,22 +184,7 @@ class Cmd
   def optflags
     args = []
     args << "-#{ENV['HOMEBREW_OPTIMIZATION_LEVEL']}"
-
-    # When bottling use the oldest supported CPU type.
-    if cccfg? 'bc'
-      # Custom bottle specified during the build
-      args << ENV['HOMEBREW_ARCHFLAGS']
-    elsif cccfg? 'bi6'
-      args << '-march=core2'
-    elsif cccfg? 'bi'
-      args << '-march=prescott'
-    elsif cccfg? 'bpA'
-      args << '-mcpu=7400'
-    elsif cccfg? 'bp'
-      args << '-mcpu=750'
-    else
-      args << '-march=native' if tool =~ /clang/
-    end
+    args.concat ENV['HOMEBREW_OPTFLAGS'].split(' ') if ENV['HOMEBREW_OPTFLAGS']
     args
   end
   def archflags

Library/Homebrew/extend/ENV/std.rb

@@ -343,7 +343,7 @@ module Stdenv
 
     if ARGV.build_bottle?
       arch = ARGV.bottle_arch || Hardware.oldest_cpu
-      append flags, Hardware::CPU.optimization_flags[arch]
+      append flags, Hardware::CPU.optimization_flags.fetch(arch)
     else
       # Don't set -msse3 and older flags because -march does that for us
       append flags, map.fetch(Hardware::CPU.family, default)

Library/Homebrew/extend/ENV/super.rb

@@ -76,30 +76,19 @@ module Superenv
     self['HOMEBREW_SDKROOT'] = "#{MacOS.sdk_path}" if MacOS::Xcode.without_clt?
     self['HOMEBREW_DEVELOPER_DIR'] = determine_developer_dir # used by our xcrun shim
     self['HOMEBREW_VERBOSE'] = "1" if ARGV.verbose?
+    self['HOMEBREW_OPTFLAGS'] = determine_optflags
     self['CMAKE_PREFIX_PATH'] = determine_cmake_prefix_path
     self['CMAKE_FRAMEWORK_PATH'] = determine_cmake_frameworks_path
     self['CMAKE_INCLUDE_PATH'] = determine_cmake_include_path
     self['CMAKE_LIBRARY_PATH'] = determine_cmake_library_path
     self['ACLOCAL_PATH'] = determine_aclocal_path
 
-    # For custom bottles, need to specify the arch in the environment
-    # so that the compiler shims have access
-    if (arch = ARGV.bottle_arch)
-      self['HOMEBREW_ARCHFLAGS'] = Hardware::CPU.optimization_flags[arch]
-    end
-
     # The HOMEBREW_CCCFG ENV variable is used by the ENV/cc tool to control
     # compiler flag stripping. It consists of a string of characters which act
     # as flags. Some of these flags are mutually exclusive.
     #
     # u - A universal build was requested
     # 3 - A 32-bit build was requested
-    # b - Installing from a bottle
-    # c - Installing from a bottle with a custom architecture
-    # i - Installing from a bottle on Intel
-    # 6 - Installing from a bottle on 64-bit Intel
-    # p - Installing from a bottle on PPC
-    # A - Installing from a bottle on PPC with Altivec
     # O - Enables argument refurbishing. Only active under the
     #     make/bsdmake wrappers currently.
     # x - Enable C++11 mode.
@@ -214,27 +203,17 @@ module Superenv
     end
   end
 
-  def determine_cccfg
-    s = ""
+  def determine_optflags
     if ARGV.build_bottle?
-      s << if ARGV.bottle_arch
-        'bc'
-      elsif Hardware::CPU.type == :intel
-        if Hardware::CPU.is_64_bit?
-          'bi6'
-        else
-          'bi'
-        end
-      elsif Hardware::CPU.type == :ppc
-        if Hardware::CPU.altivec?
-          'bpA'
-        else
-          'bp'
-        end
-      else
-        'b'
-      end
+      arch = ARGV.bottle_arch || Hardware.oldest_cpu
+      Hardware::CPU.optimization_flags.fetch(arch)
+    elsif compiler == :clang
+      "-march=native"
     end
+  end
+
+  def determine_cccfg
+    s = ""
     # Fix issue with sed barfing on unicode characters on Mountain Lion
     s << 's' if MacOS.version >= :mountain_lion
     # Fix issue with >= 10.8 apr-1-config having broken paths