Merge bitcoin/bitcoin#30451: depends: remove Darwin ENV unsetting

bda537f7c4 depends: remove ENV unsetting for darwin (fanquake)
1807760f09 guix: improve ENV unsetting for macOS (fanquake)
0b2aeee21d depends: patch explicit -lm usage out of Qt tools (fanquake)

Pull request description:

  Now that we use the native compiler, and have fixed Qt, and these vars
  are (almost) unset in Guix, we can remove the unsetting from our compiler
  command here.

  I couldn't manage to make a darwin-clang-cross only exclusion of `-lm` work properly
  for Qt, so opted for just removing the explicit link entirely. I do not think this should have
  any other unwanted side-effects.

  Fixes #21552.

ACKs for top commit:
  TheCharlatan:
    ACK bda537f7c4

Tree-SHA512: 97a2d85de7d4b1d65717ecb521399ecba5f53863b8aef21af62ede5ceee59ee1a9392663da3a3852cad1b6d8b420dd4b0b5f0eea38d30a81785d8b2718620b5f

contrib/guix/libexec/build.sh

@@ -71,11 +71,9 @@ unset OBJCPLUS_INCLUDE_PATH
 
 export C_INCLUDE_PATH="${NATIVE_GCC}/include"
 export CPLUS_INCLUDE_PATH="${NATIVE_GCC}/include/c++:${NATIVE_GCC}/include"
-export OBJC_INCLUDE_PATH="${NATIVE_GCC}/include"
-export OBJCPLUS_INCLUDE_PATH="${NATIVE_GCC}/include/c++:${NATIVE_GCC}/include"
 
 case "$HOST" in
-    *darwin*) export LIBRARY_PATH="${NATIVE_GCC}/lib" ;;
+    *darwin*) export LIBRARY_PATH="${NATIVE_GCC}/lib" ;; # Required for qt/qmake
     *mingw*) export LIBRARY_PATH="${NATIVE_GCC}/lib" ;;
     *)
         NATIVE_GCC_STATIC="$(store_path gcc-toolchain static)"
@@ -180,6 +178,14 @@ make -C depends --jobs="$JOBS" HOST="$HOST" \
                                    x86_64_linux_NM=x86_64-linux-gnu-gcc-nm \
                                    x86_64_linux_STRIP=x86_64-linux-gnu-strip
 
+case "$HOST" in
+    *darwin*)
+        # Unset now that Qt is built
+        unset C_INCLUDE_PATH
+        unset CPLUS_INCLUDE_PATH
+        unset LIBRARY_PATH
+        ;;
+esac
 
 ###########################
 # Source Tarball Building #

depends/hosts/darwin.mk

@@ -50,17 +50,11 @@ darwin_STRIP=$(shell $(SHELL) $(.SHELLFLAGS) "command -v llvm-strip")
 #         Disable adhoc codesigning (for now) when using LLVM tooling, to avoid
 #         non-determinism issues with the Identifier field.
 
-darwin_CC=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
-              -u OBJC_INCLUDE_PATH -u OBJCPLUS_INCLUDE_PATH -u CPATH \
-              -u LIBRARY_PATH \
-              $(clang_prog) --target=$(host) \
+darwin_CC=$(clang_prog) --target=$(host) \
               -isysroot$(OSX_SDK) -nostdlibinc \
               -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks
 
-darwin_CXX=env -u C_INCLUDE_PATH -u CPLUS_INCLUDE_PATH \
-               -u OBJC_INCLUDE_PATH -u OBJCPLUS_INCLUDE_PATH -u CPATH \
-               -u LIBRARY_PATH \
-               $(clangxx_prog) --target=$(host) \
+darwin_CXX=$(clangxx_prog) --target=$(host) \
                -isysroot$(OSX_SDK) -nostdlibinc \
                -iwithsysroot/usr/include/c++/v1 \
                -iwithsysroot/usr/include -iframeworkwithsysroot/System/Library/Frameworks

depends/packages/qt.mk

@@ -23,6 +23,7 @@ $(package)_patches += memory_resource.patch
 $(package)_patches += clang_18_libpng.patch
 $(package)_patches += utc_from_string_no_optimize.patch
 $(package)_patches += windows_lto.patch
+$(package)_patches += darwin_no_libm.patch
 $(package)_patches += zlib-timebits64.patch
 
 $(package)_qttranslations_file_name=qttranslations-$($(package)_suffix)
@@ -236,6 +237,7 @@ define $(package)_preprocess_cmds
   patch -p1 -i $($(package)_patch_dir)/utc_from_string_no_optimize.patch && \
   patch -p1 -i $($(package)_patch_dir)/guix_cross_lib_path.patch && \
   patch -p1 -i $($(package)_patch_dir)/windows_lto.patch && \
+  patch -p1 -i $($(package)_patch_dir)/darwin_no_libm.patch && \
   patch -p1 -i $($(package)_patch_dir)/zlib-timebits64.patch && \
   mkdir -p qtbase/mkspecs/macx-clang-linux &&\
   cp -f qtbase/mkspecs/macx-clang/qplatformdefs.h qtbase/mkspecs/macx-clang-linux/ &&\

depends/patches/qt/darwin_no_libm.patch

@@ -0,0 +1,17 @@
+build: remove explicit -lm link from qttools
+    
+This causes issues with at least the macOS cross build, and shouldn't
+actually be required anywhere else. GCC with libstdc++ will already get libm.
+
+--- a/qtbase/src/corelib/tools/tools.pri
++++ b/qtbase/src/corelib/tools/tools.pri
+@@ -111,9 +111,6 @@ qtConfig(easingcurve) {
+         tools/qtimeline.cpp
+ }
+ 
+-# Note: libm should be present by default becaue this is C++
+-unix:!macx-icc:!vxworks:!haiku:!integrity:!wasm: LIBS_PRIVATE += -lm
+-
+ TR_EXCLUDE += ../3rdparty/*
+ 
+ # MIPS DSP