Switch to /usr/local/src

https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s12.html

> Generally, source should not be built within this hierarchy.

Author: tianon

Diff for: Dockerfile.template

@@ -70,20 +70,20 @@ RUN set -eux; \
 	apk del --no-network .gpg-deps; \
 {{ ) end -}}
 	\
-	mkdir -p /usr/src/bash; \
+	mkdir -p /usr/local/src/bash; \
 	tar \
 		--extract \
 		--file=bash.tar.gz \
 		--strip-components=1 \
-		--directory=/usr/src/bash \
+		--directory=/usr/local/src/bash \
 	; \
 	rm bash.tar.gz; \
 	\
 	if [ -d bash-patches ]; then \
 		apk add --no-cache --virtual .patch-deps patch; \
 		for p in bash-patches/*; do \
 			patch \
-				--directory=/usr/src/bash \
+				--directory=/usr/local/src/bash \
 				--input="$(readlink -f "$p")" \
 				--strip=0 \
 			; \
@@ -95,11 +95,11 @@ RUN set -eux; \
 {{ if env.version == "devel" then ( -}}
 	\
 # https://lists.gnu.org/archive/html/bug-bash/2023-05/msg00011.html
-	{ echo '#include <unistd.h>'; echo; cat /usr/src/bash/lib/sh/strscpy.c; } > /usr/src/bash/lib/sh/strscpy.c.new; \
-	mv /usr/src/bash/lib/sh/strscpy.c.new /usr/src/bash/lib/sh/strscpy.c; \
+	{ echo '#include <unistd.h>'; echo; cat /usr/local/src/bash/lib/sh/strscpy.c; } > /usr/local/src/bash/lib/sh/strscpy.c.new; \
+	mv /usr/local/src/bash/lib/sh/strscpy.c.new /usr/local/src/bash/lib/sh/strscpy.c; \
 {{ ) else "" end -}}
 	\
-	cd /usr/src/bash; \
+	cd /usr/local/src/bash; \
 	gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)"; \
 {{ if env.version == "devel" or (env.version | split(".") | .[0] | tonumber) >= 5 then "" else ( -}}
 # update "config.guess" and "config.sub" to get more aggressively inclusive architecture support
@@ -130,7 +130,7 @@ RUN set -eux; \
 	make -j "$(nproc)"; \
 	make install; \
 	cd /; \
-	rm -r /usr/src/bash; \
+	rm -r /usr/local/src/bash; \
 	\
 # delete a few installed bits for smaller image size
 	rm -rf \