[RISCV][NFC] Add isTargetAndroid API in RISCVSubtarget (#87671)

This is required to set target specific code generation options for
Android,
like using the TLS slot for the stack protector.

Author: ilovepi

llvm/lib/Target/RISCV/RISCVSubtarget.h

@@ -254,6 +254,7 @@ class RISCVSubtarget : public RISCVGenSubtargetInfo {
   const LegalizerInfo *getLegalizerInfo() const override;
   const RegisterBankInfo *getRegBankInfo() const override;
 
+  bool isTargetAndroid() const { return getTargetTriple().isAndroid(); }
   bool isTargetFuchsia() const { return getTargetTriple().isOSFuchsia(); }
 
   bool useConstantPoolForLargeInts() const;