Adjust doc and add release note for the macOS ARCHFLAGS change.

Author: anthony-tuininga

doc/src/release_notes.rst

@@ -34,6 +34,9 @@ Thick Mode Changes
 Common Changes
 ++++++++++++++
 
+#)  The compiler flag ``-arch x86_64`` no longer needs to be explicitly
+    specified when building from source code on macOS (Intel x86) without
+    Universal Python binaries.
 #)  Improved samples and documentation.
 
 

doc/src/user_guide/installation.rst

@@ -757,11 +757,6 @@ code:
 
 - C Compiler: A C99 compiler is needed.
 
-On macOS, use a Python Universal 2 binary, or set an explicit architecture to
-match your environment.  For example, execute ``export ARCHFLAGS="-arch
-x86_64"`` before building the source code on macOS Intel x86.  Without this,
-the build may succeed but the package will fail to import in Python.
-
 Install Using GitHub
 --------------------