gh-109575: Don't export -fsanitize compiler options

When Python is configured to use ASAN, MSAN or UBSAN sanitizer, with
"./configure --with-address-sanitizer" for example, compiler and
linker flags for sanitizers are no longer exported to third party C
extensions. Add flags to CFLAGS_NODIST and LDFLAGS_NODIST, instead of
BASECFLAGS and LDFLAGS.

Author: vstinner

Misc/NEWS.d/next/Build/2023-09-19-16-32-56.gh-issue-109575.41o1jt.rst

@@ -0,0 +1,5 @@
+When Python is configured to use ASAN, MSAN or UBSAN sanitizer, with
+``./configure --with-address-sanitizer`` for example, compiler and linker
+flags for sanitizers are no longer exported to third party C extensions. Add
+flags to ``CFLAGS_NODIST`` and ``LDFLAGS_NODIST``, instead of ``BASECFLAGS``
+and ``LDFLAGS``.  Patch by Victor Stinner.

configure

@@ -2997,8 +2997,8 @@ AC_ARG_WITH([address_sanitizer],
                            [enable AddressSanitizer memory error detector, 'asan' (default is no)]),
 [
 AC_MSG_RESULT([$withval])
-BASECFLAGS="-fsanitize=address -fno-omit-frame-pointer $BASECFLAGS"
-LDFLAGS="-fsanitize=address $LDFLAGS"
+CFLAGS_NODIST="$CFLAGS_NODIST -fsanitize=address -fno-omit-frame-pointer"
+LDFLAGS_NODIST="$LDFLAGS_NODIST -fsanitize=address"
 # ASan works by controlling memory allocation, our own malloc interferes.
 with_pymalloc="no"
 ],
@@ -3014,8 +3014,8 @@ AC_ARG_WITH(
 [
 AC_MSG_RESULT([$withval])
 AX_CHECK_COMPILE_FLAG([-fsanitize=memory],[
-BASECFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 -fno-omit-frame-pointer $BASECFLAGS"
-LDFLAGS="-fsanitize=memory -fsanitize-memory-track-origins=2 $LDFLAGS"
+CFLAGS_NODIST="$CFLAGS_NODIST -fsanitize=memory -fsanitize-memory-track-origins=2 -fno-omit-frame-pointer"
+LDFLAGS_NODIST="$LDFLAGS_NODIST -fsanitize=memory -fsanitize-memory-track-origins=2"
 ],[AC_MSG_ERROR([The selected compiler doesn't support memory sanitizer])])
 # MSan works by controlling memory allocation, our own malloc interferes.
 with_pymalloc="no"
@@ -3031,8 +3031,8 @@ AC_ARG_WITH(
   )],
 [
 AC_MSG_RESULT([$withval])
-BASECFLAGS="-fsanitize=undefined $BASECFLAGS"
-LDFLAGS="-fsanitize=undefined $LDFLAGS"
+CFLAGS_NODIST="$CFLAGS_NODIST -fsanitize=undefined"
+LDFLAGS_NODIST="$LDFLAGS_NODIST -fsanitize=undefined"
 with_ubsan="yes"
 ],
 [