superenv: disable ConstraintEliminationPass on Xcode 16

This can result in build failures (e.g. OpenJDK) and silently miscompile
some formulae (e.g. Vim).

See Homebrew/homebrew-core#195325.

Library/Homebrew/extend/ENV/super.rb

@@ -120,6 +120,7 @@ def setup_build_environment(formula: nil, cc: nil, build_bottle: false, bottle_a
     # o - Pass `-oso_prefix` to `ld` whenever it is invoked
     # c - Pass `-ld_classic` to `ld` whenever it is invoked
     #     with `-dead_strip_dylibs`
+    # E - Pass `-mllvm -enable-constraint-elimination=0` to clang.
     #
     # These flags will also be present:
     # a - apply fix for apr-1-config path

Library/Homebrew/extend/os/mac/extend/ENV/shared.rb

@@ -39,4 +39,16 @@ def no_fixup_chains_support?
     # https://en.wikipedia.org/wiki/Xcode#Xcode_11.0_-_14.x_(since_SwiftUI_framework)_2
     OS::Mac::DevelopmentTools.ld64_version >= 711
   end
+
+  # ConstraintEliminiationPass can silently miscompile some formulae.
+  # https://github.com/Homebrew/homebrew-core/issues/195325
+  sig { returns(T::Boolean) }
+  def disable_contraint_elimination?
+    return false if compiler != :clang
+
+    return false if !MacOS::Xcode.version.null? && MacOS::Xcode.version.major != 16
+    return false if !MacOS::CLT.version.null? && MacOS::CLT.version.major != 16
+
+    true
+  end
 end

Library/Homebrew/extend/os/mac/extend/ENV/std.rb

@@ -114,4 +114,8 @@ def no_weak_imports
   def no_fixup_chains
     append "LDFLAGS", "-Wl,-no_fixup_chains" if no_fixup_chains_support?
   end
+
+  def disable_constraint_elimination_if_needed
+    append_to_cflags "-mllvm -enable-constraint-elimination=0" if disable_contraint_elimination?
+  end
 end

Library/Homebrew/extend/os/mac/extend/ENV/super.rb

@@ -159,6 +159,9 @@ def setup_build_environment(formula: nil, cc: nil, build_bottle: false, bottle_a
     if OS::Mac::DevelopmentTools.ld64_version >= "1015.7" && OS::Mac::DevelopmentTools.ld64_version <= "1022.1"
       append_to_cccfg "c"
     end
+
+    # https://github.com/Homebrew/homebrew-core/issues/195325
+    disable_constraint_elimination_if_needed
   end
 
   def no_weak_imports
@@ -168,4 +171,8 @@ def no_weak_imports
   def no_fixup_chains
     append_to_cccfg "f" if no_fixup_chains_support?
   end
+
+  def disable_constraint_elimination_if_needed
+    append_to_cccfg "E" if disable_contraint_elimination?
+  end
 end

Library/Homebrew/shims/super/cc

@@ -299,6 +299,7 @@ class Cmd
     args.concat(archflags)
     args << "-std=#{@arg0}" if /c[89]9/.match?(@arg0)
     args << "-g" if debug_symbols?
+    args += ["-mllvm", "-enable-constraint-elimination=0"] if disable_contraint_elimination?
     args
   end
 
@@ -435,6 +436,10 @@ class Cmd
          .flat_map { |arg| arg.delete_prefix("-Wl,").split(",") }
   end
 
+  def disable_contraint_elimination?
+    config.include?("E")
+  end
+
   def no_fixup_chains?
     return false unless config.include?("f")
     return false unless calls_ld?