build: resolve SCHEME from $(JERBOA_HOME)/.chez/bin/scheme

ober

bae2d2c5163cae151bc7cb4f137bd0903e202080

diff --git a/Makefile b/Makefile
index 885d3c5..2c67f5d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,13 @@
-SCHEME     = scheme
 JERBOA_HOME ?= $(HOME)/mine/jerboa
+SCHEME     ?= $(JERBOA_HOME)/.chez/bin/scheme
 LIBDIRS    = --libdirs $(JERBOA_HOME)/lib:./lib:vendor/chez-sqlite/src:vendor/jerboa-websearch/src
 JERBUILD   = $(SCHEME) --libdirs $(JERBOA_HOME)/lib --script $(JERBOA_HOME)/jerbuild.ss
 
+# Fail early with a clear pointer if the jerboa-local Chez build is missing.
+ifeq ($(wildcard $(SCHEME)),)
+$(error Chez Scheme not found at $(SCHEME). Run 'make chez' in $(JERBOA_HOME) (or set SCHEME=... to override).)
+endif
+
 # Library paths for FFI shared objects (macOS: dylib, Linux: so)
 SQLITE_LIB_DIR := $(shell brew --prefix sqlite 2>/dev/null)/lib
 SHIM_DIR       := $(CURDIR)/vendor/chez-sqlite
diff --git a/build-jcode-musl.sh b/build-jcode-musl.sh
index 3d2c2a2..d0c8216 100755
--- a/build-jcode-musl.sh
+++ b/build-jcode-musl.sh
@@ -17,6 +17,13 @@ SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 HOME_DIR="${HOME:-/root}"
 JERBOA_HOME="${JERBOA_HOME:-${HOME_DIR}/mine/jerboa}"
 JERBOA_LIB="${JERBOA_HOME}/lib"
+SCHEME="${SCHEME:-${JERBOA_HOME}/.chez/bin/scheme}"
+
+if [ ! -x "${SCHEME}" ]; then
+    echo "ERROR: Chez Scheme not found at ${SCHEME}" >&2
+    echo "       Run 'make chez' in ${JERBOA_HOME} (or set SCHEME=... to override)." >&2
+    exit 1
+fi
 
 echo "==================================="
 echo "Building jcode with musl libc (static)"
@@ -67,7 +74,7 @@ fi
 
 # Validate musl toolchain via jerboa
 echo "[1/2] Validating musl toolchain via jerboa..."
-scheme -q --libdirs "${JERBOA_LIB}" <<'VALIDATE'
+"${SCHEME}" -q --libdirs "${JERBOA_LIB}" <<'VALIDATE'
 (import (chezscheme) (jerboa build musl))
 (let ([result (validate-musl-setup)])
   (printf "  ~a: ~a~n" (car result) (cdr result))
@@ -81,7 +88,7 @@ echo "[2/2] Running musl build..."
 LD_LIBRARY_PATH="${SCRIPT_DIR}/vendor/chez-sqlite:${SCRIPT_DIR}/vendor/termbox2:${JERBOA_LIB}:." \
 JERBOA_HOME="${JERBOA_HOME}" \
 JERBOA_MUSL_CHEZ_PREFIX="${MUSL_CHEZ_PREFIX}" \
-scheme -q --libdirs "${JERBOA_LIB}:./lib:vendor/chez-sqlite/src:vendor/jerboa-websearch/src" \
+"${SCHEME}" -q --libdirs "${JERBOA_LIB}:./lib:vendor/chez-sqlite/src:vendor/jerboa-websearch/src" \
     <build-jcode-musl.ss
 
 # Verify