In Alpine 3.21 bump llvm version

Fixes #1296

Author: yosifkit

12/alpine3.20/Dockerfile

@@ -1,4 +1,8 @@
-FROM alpine:{{ env.variant | ltrimstr("alpine") }}
+{{
+	def alpine_version:
+		env.variant | ltrimstr("alpine")
+-}}
+FROM alpine:{{ alpine_version }}
 
 # 70 is the standard uid/gid for "postgres" in Alpine
 # https://git.alpinelinux.org/aports/tree/main/postgresql/postgresql.pre-install?h=3.12-stable
@@ -52,7 +56,14 @@ ENV PG_MAJOR {{ env.version }}
 ENV PG_VERSION {{ .version }}
 ENV PG_SHA256 {{ .sha256 }}
 
-{{ def llvmver: "15" -}}
+{{
+	def llvmver:
+		if alpine_version | split(".") | map(tonumber) < [3, 21] then
+			"15"
+		else
+			"19"
+		end
+-}}
 ENV DOCKER_PG_LLVM_DEPS \
 		llvm{{ llvmver }}-dev \
 		clang{{ llvmver }}
@@ -117,9 +128,9 @@ RUN set -eux; \
 	wget -O config/config.guess 'https://git.savannah.gnu.org/cgit/config.git/plain/config.guess?id=7d3d27baf8107b630586c962c057e22149653deb'; \
 	wget -O config/config.sub 'https://git.savannah.gnu.org/cgit/config.git/plain/config.sub?id=7d3d27baf8107b630586c962c057e22149653deb'; \
 	\
-# https://git.alpinelinux.org/aports/tree/community/postgresql12/APKBUILD?h=3.18-stable&id=a470294e6d6ca7059e41c54769b7c3c26ec901d4#n158
+# https://git.alpinelinux.org/aports/tree/community/postgresql15/APKBUILD?h=3.21-stable&id=40544ade947bec1798edb0f749f4e967e842624b#n172
 	export LLVM_CONFIG="/usr/lib/llvm{{ llvmver }}/bin/llvm-config"; \
-# https://git.alpinelinux.org/aports/tree/community/postgresql12/APKBUILD?h=3.18-stable&id=a470294e6d6ca7059e41c54769b7c3c26ec901d4#n163
+# https://git.alpinelinux.org/aports/tree/community/postgresql15/APKBUILD?h=3.21-stable&id=40544ade947bec1798edb0f749f4e967e842624b#n177
 	export CLANG=clang-{{ llvmver }}; \
 	\
 # configure options taken from: