python, python3: fix Tk error.

Fix RuntimeError: tk.h version (8.6) doesn't match libtk.a version (8.5)

The problem was that CPPFLAGS and LDFLAGS for brewed Tk were specified
to environment variable but Python (seems) prefer the CPPFLAGS in
arguments specified to './configure', mean
"-I#{MacOS.sdk_path}/usr/include" version is used.

Closes #18657.
Closes #41728.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Formula/python.rb

@@ -110,18 +110,20 @@ def install
 
     args << "--without-gcc" if ENV.compiler == :clang
 
+    cflags   = []
+    ldflags  = []
+    cppflags = []
+
     unless MacOS::CLT.installed?
       # Help Python's build system (setuptools/pip) to build things on Xcode-only systems
       # The setup.py looks at "-isysroot" to get the sysroot (and not at --sysroot)
-      cflags = "CFLAGS=-isysroot #{MacOS.sdk_path}"
-      ldflags = "LDFLAGS=-isysroot #{MacOS.sdk_path}"
-      args << "CPPFLAGS=-I#{MacOS.sdk_path}/usr/include" # find zlib
+      cflags   << "-isysroot #{MacOS.sdk_path}"
+      ldflags  << "-isysroot #{MacOS.sdk_path}"
+      cppflags << "-I#{MacOS.sdk_path}/usr/include" # find zlib
       # For the Xlib.h, Python needs this header dir with the system Tk
       if build.without? "tcl-tk"
-        cflags += " -I#{MacOS.sdk_path}/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers"
+        cflags << "-I#{MacOS.sdk_path}/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers"
       end
-      args << cflags
-      args << ldflags
     end
 
     # Avoid linking to libgcc https://code.activestate.com/lists/python-dev/112195/
@@ -157,10 +159,14 @@ def install
 
     if build.with? "tcl-tk"
       tcl_tk = Formula["homebrew/dupes/tcl-tk"].opt_prefix
-      ENV.append "CPPFLAGS", "-I#{tcl_tk}/include"
-      ENV.append "LDFLAGS", "-L#{tcl_tk}/lib"
+      cppflags << "-I#{tcl_tk}/include"
+      ldflags  << "-L#{tcl_tk}/lib"
     end
 
+    args << "CFLAGS=#{cflags.join(' ')}"     unless cflags.empty?
+    args << "LDFLAGS=#{ldflags.join(' ')}"   unless ldflags.empty?
+    args << "CPPFLAGS=#{cppflags.join(' ')}" unless cppflags.empty?
+
     system "./configure", *args
 
     # HAVE_POLL is "broken" on OS X. See:

Library/Formula/python3.rb

@@ -109,17 +109,20 @@ def install
 
     args << "--without-gcc" if ENV.compiler == :clang
 
+    cflags   = []
+    ldflags  = []
+    cppflags = []
+
     unless MacOS::CLT.installed?
       # Help Python's build system (setuptools/pip) to build things on Xcode-only systems
       # The setup.py looks at "-isysroot" to get the sysroot (and not at --sysroot)
-      cflags = "CFLAGS=-isysroot #{MacOS.sdk_path}"
-      ldflags = "LDFLAGS=-isysroot #{MacOS.sdk_path}"
-      args << "CPPFLAGS=-I#{MacOS.sdk_path}/usr/include" # find zlib
+      cflags   << "-isysroot #{MacOS.sdk_path}"
+      ldflags  << "-isysroot #{MacOS.sdk_path}"
+      cppflags << "-I#{MacOS.sdk_path}/usr/include" # find zlib
+      # For the Xlib.h, Python needs this header dir with the system Tk
       if build.without? "tcl-tk"
-        cflags += " -I#{MacOS.sdk_path}/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers"
+        cflags << "-I#{MacOS.sdk_path}/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers"
       end
-      args << cflags
-      args << ldflags
     end
     # Avoid linking to libgcc http://code.activestate.com/lists/python-dev/112195/
     args << "MACOSX_DEPLOYMENT_TARGET=#{MacOS.version}"
@@ -150,10 +153,14 @@ def install
 
     if build.with? "tcl-tk"
       tcl_tk = Formula["tcl-tk"].opt_prefix
-      ENV.append "CPPFLAGS", "-I#{tcl_tk}/include"
-      ENV.append "LDFLAGS", "-L#{tcl_tk}/lib"
+      cppflags << "-I#{tcl_tk}/include"
+      ldflags  << "-L#{tcl_tk}/lib"
     end
 
+    args << "CFLAGS=#{cflags.join(' ')}"     unless cflags.empty?
+    args << "LDFLAGS=#{ldflags.join(' ')}"   unless ldflags.empty?
+    args << "CPPFLAGS=#{cppflags.join(' ')}" unless cppflags.empty?
+
     system "./configure", *args
 
     system "make"