What is the building for the r90 pennant?
CREATE TABLE "ch_or_12th_emergency_flotilla" (
  "name" text,
  "pennant" text,
  "builder" text,
  "laid_down" text,
  "launched" text,
  "commissioned" text
);
SELECT "builder" FROM "ch_or_12th_emergency_flotilla" WHERE "pennant"='r90';