guix, refactor: Move duplicated `profiledir_for_host()` to `prelude.bash`

diff --git a/contrib/guix/guix-build b/contrib/guix/guix-build
index 9c78c2a2..a02c3603 100755
--- a/contrib/guix/guix-build
+++ b/contrib/guix/guix-build
@@ -294,14 +294,6 @@ for host in $HOSTS; do
     make -C "${PWD}/depends" -j"$JOBS" download-"$(host_to_commonname "$host")" ${V:+V=1} ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"}
 done
 
-# Usage: profiledir_for_host HOST SUFFIX
-#
-#   HOST: The current platform triple we're building for
-#
-profiledir_for_host() {
-    echo "${PROFILES_BASE}/${1}${2:+-${2}}"
-}
-
 
 #########
 # BUILD #
diff --git a/contrib/guix/guix-codesign b/contrib/guix/guix-codesign
index 230499c0..f985fd4c 100755
--- a/contrib/guix/guix-codesign
+++ b/contrib/guix/guix-codesign
@@ -223,14 +223,6 @@ SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(git -c log.showSignature=false log --f
 OUTDIR_BASE="${OUTDIR_BASE:-${VERSION_BASE}/output}"
 mkdir -p "$OUTDIR_BASE"
 
-# Usage: profiledir_for_host HOST SUFFIX
-#
-#   HOST: The current platform triple we're building for
-#
-profiledir_for_host() {
-    echo "${PROFILES_BASE}/${1}${2:+-${2}}"
-}
-
 #########
 # BUILD #
 #########
diff --git a/contrib/guix/libexec/prelude.bash b/contrib/guix/libexec/prelude.bash
index fbebd2a1..c13f24c5 100644
--- a/contrib/guix/libexec/prelude.bash
+++ b/contrib/guix/libexec/prelude.bash
@@ -89,6 +89,15 @@ outdir_for_host() {
     echo "${OUTDIR_BASE}/${1}${2:+-${2}}"
 }
 
+# Usage: profiledir_for_host HOST [SUFFIX]
+#
+#   HOST: The current platform triple we're building for
+#   SUFFIX: Optional. If provided, appended to the directory name as "-SUFFIX"
+#
+profiledir_for_host() {
+    echo "${PROFILES_BASE}/${1}${2:+-${2}}"
+}
+
 ################
 # Set common variables
 ################