extend/ENV/super: set CC/CXX to real names for llvm_clang

[cho-m]

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CC=llvm_clang/CXX=llvm_clang++ can cause issues in formulae if the value of CC/CXX is saved into binaries/scripts to be used at runtime. This PR follows similar pattern in my versioned GCC PR (#22889) so that the build scripts will see the actual name of the command, i.e. CC=clang/CXX=clang++.

This is also similar to how we handle swift shim:

brew/Library/Homebrew/shims/super/swift

Lines 5 to 10 in 8d94d5c

	export CC="clang"
	export CXX="clang++"
	# swift_clang isn't a shim but is used to ensure the cc shim
	# points to the compiler inside the swift keg
	export HOMEBREW_CC="swift_clang"

To make this work, need to adjust cc shim too so that it handles LLVM Clang the same as all other compilers. Previously, it would only apply LLVM's clang++ when named llvm_clang++. Now, even if compiler is invoked as clang++, g++, etc., brew should use HOMEBREW_CC=llvm_clang forward to LLVM's clang++.

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This should avoid workarounds like

• https://github.com/Homebrew/homebrew-core/blob/58a1d9aff4768c36851ad2fb49f09c4ceeababef/Formula/e/ecl.rb#L44-L45

I tried removing above and running brew install --cc llvm_clang ecl. Snippets of output:

checking for gcc... clang
...
libtool: compile:  clang -fPIC -fno-common -DHAVE_CONFIG_H -I../src -I/private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5/src/bdwgc/libatomic_ops/src -I/opt/homebrew/opt/gmp/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/include -I/opt/homebrew/opt/bdw-gc/include -fPIC -Wall -Wextra -Wpedantic -Wno-long-long -g -O0 -fPIC -fno-common -D_THREAD_SAFE -MT atomic_ops.lo -MD -MP -MF .deps/atomic_ops.Tpo -c /private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5/src/bdwgc/libatomic_ops/src/atomic_ops.c  -fno-common -DPIC -o atomic_ops.o

And underlying 02.make.cc.log:

clang called with: -fPIC -fno-common -DHAVE_CONFIG_H -I../src -I/private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5/src/bdwgc/libatomic_ops/src -I/opt/homebrew/opt/gmp/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/include -I/opt/homebrew/opt/bdw-gc/include -fPIC -Wall -Wextra -Wpedantic -Wno-long-long -g -O0 -fPIC -fno-common -D_THREAD_SAFE -MT atomic_ops.lo -MD -MP -MF .deps/atomic_ops.Tpo -c /private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5/src/bdwgc/libatomic_ops/src/atomic_ops.c -fno-common -DPIC -o atomic_ops.o
superenv removed:  -Wall -Wextra -Wpedantic -g -O0
superenv added:    -w -Os -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk --sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk -isystem/opt/homebrew/include -isystem/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers -fdebug-prefix-map=/private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5=.
superenv executed: /opt/homebrew/opt/llvm/bin/clang -w -Os -fPIC -fno-common -DHAVE_CONFIG_H -I../src -I/private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5/src/bdwgc/libatomic_ops/src -I/opt/homebrew/opt/gmp/include -I/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/include -I/opt/homebrew/opt/bdw-gc/include -fPIC -Wno-long-long -fPIC -fno-common -D_THREAD_SAFE -MT atomic_ops.lo -MD -MP -MF .deps/atomic_ops.Tpo -c /private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5/src/bdwgc/libatomic_ops/src/atomic_ops.c -fno-common -DPIC -o atomic_ops.o -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk --sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk -isystem/opt/homebrew/include -isystem/Library/Developer/CommandLineTools/SDKs/MacOSX26.sdk/System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers -fdebug-prefix-map=/private/tmp/ecl-20260702-80027-mytn21/ecl-26.5.5=.

[Copilot]

Pull request overview

This PR adjusts Superenv’s llvm_clang compiler setup so that CC/CXX/OBJC/OBJCXX are set to the “real” compiler names (clang/clang++) while keeping HOMEBREW_CC=llvm_clang so Homebrew’s superenv shims still route builds through the LLVM toolchain when desired.

Changes:

• Override Superenv#llvm_clang to set CC/CXX (and ObjC variants) to clang/clang++ after the standard superenv compiler selection.
• Update the superenv cc shim to consistently choose LLVM’s clang++ when HOMEBREW_CC=llvm_clang, even if invoked under other *++ names.
• Add a unit spec verifying the llvm_clang environment variable behavior in Superenv.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/extend/ENV/super.rb	Overrides llvm_clang to rewrite CC/CXX/OBJC/OBJCXX to clang/clang++ while preserving HOMEBREW_CC.
Library/Homebrew/shims/super/cc	Removes the special-case llvm_(clang...) tool selection and instead routes *++ invocations to LLVM clang++ when HOMEBREW_CC=llvm_clang.
Library/Homebrew/test/ENV_spec.rb	Adds coverage for Superenv’s llvm_clang environment variable values.

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