ignore previously failed gems

bulk-compiler.sh

@@ -13,6 +13,10 @@ find build/ -type f |
   while read BUILD BUILT GEM_NAME GEM_VERSION; do
     test -f "${BUILT}" && continue
 
+    FAILED="failed/${ALPINE_VERSION}/${GEM_NAME}/${GEM_VERSION}"
+
+    test -f "${FAILED}" && continue
+
     unset EXTRA_PKGS EXTRA_GEMS GEM_COMPILER_FLAGS
 
     source "${BUILD}"
@@ -29,7 +33,7 @@ find build/ -type f |
     /usr/local/bin/bootstrap || true
 
     if test $? -ne 0 ; then
-      BUILT="failed/${ALPINE_VERSION}/${GEM_NAME}/${GEM_VERSION}"
+      BUILT="${FAILED}"
     fi
 
     dirname "${BUILT}" | xargs mkdir -p