diff --git a/scripts/xtensa-build-all.sh b/scripts/xtensa-build-all.sh
index 981ad81ff..f12bf197b 100755
--- a/scripts/xtensa-build-all.sh
+++ b/scripts/xtensa-build-all.sh
@@ -392,6 +392,8 @@ do
 	then
 		TOOLCHAIN=xt
 		ROOT="$XTENSA_BUILDS_DIR/$XTENSA_CORE/xtensa-elf"
+		# CMake cannot set (evil) build-time environment variables at configure time:
+# https://gitlab.kitware.com/cmake/community/-/wikis/FAQ#how-can-i-get-or-set-environment-variables
 		export XTENSA_SYSTEM=$XTENSA_BUILDS_DIR/$XTENSA_CORE/config
 		printf 'XTENSA_SYSTEM=%s\n' "${XTENSA_SYSTEM}"
 		PATH=$XTENSA_TOOLS_DIR/XtensaTools/bin:$OLDPATH
diff --git a/scripts/xtensa-build-zephyr.py b/scripts/xtensa-build-zephyr.py
index 992491987..256158e2f 100755
--- a/scripts/xtensa-build-zephyr.py
+++ b/scripts/xtensa-build-zephyr.py
@@ -464,7 +464,9 @@ def build_platforms():
 			print(f"XTENSA_TOOLCHAIN_PATH={XTENSA_TOOLCHAIN_PATH}")
 			print(f"TOOLCHAIN_VER={TOOLCHAIN_VER}")
 
-			# set variables expected by xcc toolchain
+			# Set variables expected by xcc toolchain. CMake cannot set (evil) build-time
+			# environment variables at configure time:
+			# https://gitlab.kitware.com/cmake/community/-/wikis/FAQ#how-can-i-get-or-set-environment-variables
 			XTENSA_BUILDS_DIR=str(pathlib.Path(xtensa_tools_root_dir, "install", "builds",
 				TOOLCHAIN_VER).absolute())
 			XTENSA_SYSTEM = str(pathlib.Path(XTENSA_BUILDS_DIR, XTENSA_CORE, "config").absolute())