core-init-ext: add more checking and verbose errors to checkPhase

src/core-init-ext.nix

@@ -79,6 +79,18 @@ in stdenv.mkDerivation (finalAttrs: {
   checkPhase = ''
     runHook preCheck
 
+    for ext in ${lib.escapeShellArgs (builtins.catAttrs "library" extensions)}; do
+      if [ ! -f "$ext" ]; then
+        echo "Extension $ext does not exist."
+        exit 1
+      fi
+
+      if ! file "$ext" | grep -qE "ELF|ar archive"; then
+        echo "Extension $ext does not appear to be a valid shared library or static archive."
+        exit 1
+      fi
+    done
+
     for ext in ${lib.escapeShellArgs (builtins.catAttrs "library" extensions)}; do
       if nm -g --defined-only "$ext" | grep -q " sqlite_api$"; then
         echo "Extension $ext appears to reference the 'sqlite_api' symbol, which is not expected for extensions which are going to be statically linked."
@@ -92,8 +104,11 @@ in stdenv.mkDerivation (finalAttrs: {
     ${lib.concatMapStringsSep "\n" (ext: "expectedSymbols[${lib.escapeShellArg ext.shutdown}]=${lib.escapeShellArg ext.library};") (lib.filter (ext: ext.shutdown or null != null) extensions)}
 
     for sym in "''${!expectedSymbols[@]}"; do
-      if ! nm -g --defined-only "''${expectedSymbols[$sym]}" | grep -q " ''${sym}$"; then
+      SYMBOL_LIST=$(nm -g --defined-only "''${expectedSymbols[$sym]}" | awk '{print $3}' | sed '/^[[:space:]]*$/d')
+      if ! grep -q "''${sym}$" <<< "$SYMBOL_LIST"; then
         echo "Expected symbol $sym not found in ''${expectedSymbols[$sym]}."
+        echo "Found symbols:"
+        echo "$SYMBOL_LIST"
         exit 1
       fi
     done