Use available jerbuild for static jsh staging

ober

c9b2c90d44999fa714d0c6bd080622b6418dec80

diff --git a/Makefile b/Makefile
index 45a235c..6aedfe6 100644
--- a/Makefile
+++ b/Makefile
@@ -1314,7 +1314,8 @@ MUSL_SCINTILLA_LIBDIR ?= /tmp/jemacs-build/jerboa-scintilla
 MUSL_JSH_ROOT ?= $(MUSL_DEPS)/jerboa-shell
 MUSL_JSH ?= $(MUSL_JSH_ROOT)/src
 MUSL_JSQLITE_STAGE ?= $(MUSL_JSH_ROOT)/_jerbuild-stage
-MUSL_JERBUILD ?= $(MUSL_JERBOA)/dist/jerbuild
+MUSL_JERBUILD ?= $(shell if [ -x "$(MUSL_JERBOA)/dist/jerbuild" ]; then printf '%s\n' "$(MUSL_JERBOA)/dist/jerbuild"; elif command -v jerbuild >/dev/null 2>&1; then command -v jerbuild; fi)
+MUSL_JERBUILD_ARG = $(if $(MUSL_JERBUILD),JERBUILD="$(MUSL_JERBUILD)")
 MUSL_JSH_MAKE_ARGS = VENDOR="$(abspath $(MUSL_JSH_ROOT)/vendor)" JSQLITE_REPO="$(abspath $(MUSL_DEPS)/jsqlite)" JSQLITE_DIR="$(abspath $(MUSL_DEPS)/jsqlite/src)" JERBOA_WORMHOLE="$(abspath $(MUSL_JSH_ROOT)/vendor/jerboa-wormhole)"
 MUSL_SCI_VENDOR ?= $(SCINTILLA_VENDOR)
 QT_STATIC_PREFIX ?= /opt/qt6-static
@@ -1346,9 +1347,9 @@ linux-tui-local: vendor-deps
 	rm -f $(MUSL_JERBOA)/lib/jerboa/*.wpo
 	$(MUSL_SCHEME) --libdirs $(MUSL_JERBOA)/lib --script $(MUSL_JERBOA)/jerbuild.ss src/ lib/
 	sh scripts/patch-jerboa-shell-compat.sh "$(CURDIR)"
-	$(MAKE) -C $(MUSL_JSH_ROOT) JERBUILD="$(MUSL_JERBUILD)" $(MUSL_JSH_MAKE_ARGS) stage-jsqlite
-	$(MAKE) -C $(MUSL_JSH_ROOT) JERBUILD="$(MUSL_JERBUILD)" $(MUSL_JSH_MAKE_ARGS) jerboa
-	$(MAKE) -C $(MUSL_JSH_ROOT) JERBUILD="$(MUSL_JERBUILD)" $(MUSL_JSH_MAKE_ARGS) gen-embed </dev/null
+	$(MAKE) -C $(MUSL_JSH_ROOT) $(MUSL_JERBUILD_ARG) $(MUSL_JSH_MAKE_ARGS) stage-jsqlite
+	$(MAKE) -C $(MUSL_JSH_ROOT) $(MUSL_JERBUILD_ARG) $(MUSL_JSH_MAKE_ARGS) jerboa
+	$(MAKE) -C $(MUSL_JSH_ROOT) $(MUSL_JERBUILD_ARG) $(MUSL_JSH_MAKE_ARGS) gen-embed </dev/null
 	rm -rf $(MUSL_PCRE2_LIBDIR) $(MUSL_SCINTILLA_LIBDIR)
 	mkdir -p $(MUSL_PCRE2_LIBDIR) $(MUSL_SCINTILLA_LIBDIR)
 	cp $(MUSL_PCRE2)/jerboa_pcre2_shim.c $(MUSL_PCRE2_LIBDIR)/pcre2_shim.c
@@ -1454,9 +1455,9 @@ linux-qt-local: vendor-deps
 	rm -f $(MUSL_JERBOA)/lib/jerboa/*.wpo
 	$(MUSL_SCHEME) --libdirs $(MUSL_JERBOA)/lib --script $(MUSL_JERBOA)/jerbuild.ss src/ lib/
 	sh scripts/patch-jerboa-shell-compat.sh "$(CURDIR)"
-	$(MAKE) -C $(MUSL_JSH_ROOT) JERBUILD="$(MUSL_JERBUILD)" $(MUSL_JSH_MAKE_ARGS) stage-jsqlite
-	$(MAKE) -C $(MUSL_JSH_ROOT) JERBUILD="$(MUSL_JERBUILD)" $(MUSL_JSH_MAKE_ARGS) jerboa
-	$(MAKE) -C $(MUSL_JSH_ROOT) JERBUILD="$(MUSL_JERBUILD)" $(MUSL_JSH_MAKE_ARGS) gen-embed </dev/null
+	$(MAKE) -C $(MUSL_JSH_ROOT) $(MUSL_JERBUILD_ARG) $(MUSL_JSH_MAKE_ARGS) stage-jsqlite
+	$(MAKE) -C $(MUSL_JSH_ROOT) $(MUSL_JERBUILD_ARG) $(MUSL_JSH_MAKE_ARGS) jerboa
+	$(MAKE) -C $(MUSL_JSH_ROOT) $(MUSL_JERBUILD_ARG) $(MUSL_JSH_MAKE_ARGS) gen-embed </dev/null
 	# Set up writable jerboa-qt copy from vendor (compile Scheme library)
 	mkdir -p /tmp/jemacs-build/jerboa-qt
 	cp -a vendor/jerboa-qt/. /tmp/jemacs-build/jerboa-qt/