script fix

recipes/kmer-db/build.sh

@@ -1,7 +1,16 @@
 #!/bin/bash
 
 uname_S=`uname -s 2>/dev/null || echo not`
-if [ "$uname_S" == "Darwin" ]; then brew install gcc@12;
+if [ "$uname_S" == "Darwin" ]; then
+    if ! command -v brew &> /dev/null; then
+        echo "Homebrew is required but not installed. Please install Homebrew first."
+        exit 1
+    fi
+    if ! brew install gcc@12; then
+        echo "Failed to install gcc@12. Please check your Homebrew installation and permissions."
+        exit 1
+    fi
+fi
 
 CFLAGS="$CFLAGS -I${PREFIX}/include"
 LDFLAGS="$LDFLAGS -L${PREFIX}/lib"