How would I encode RSA private key, given that I know the decimal representation of all of its components? ('n', '0x8978ee9e52ad5dee313b1401bc04d04fa3f90ca7018fc256afc67fc200390cbbL')

('p', '0xd098978cde12b9e101b519d42ca54e7dL')

('q', '0xa8b69b77f593ca8a280dcd7d757d9597L')

('e', '0x10001')

('d', '0x17e6c54214a8dcdc7585ca8834aaf796a797496607aa7660153859d02ba399a5L')

('dp', '0x7978a2a8319a0e0c6d861ca865e74db1L')

('dq', '0x38f797dd5495b7b118bf3860a1786b37L')

('qinv', '0x5116fa4d2efd8072ba7fe9e94831413fL')

How would I create a base 64 encoded RSA private key?
A commonly used way to encode RSA keys is DER which derives semantic meaning via ASN.1. You can find more detail in RFC3447. The ASN.1 syntax for a DER-encoded string looks as follows:

  Version ::= INTEGER { two-prime(0), multi(1) }
      (CONSTRAINED BY
      {-- version must be multi if otherPrimeInfos present --})

  RSAPrivateKey ::= SEQUENCE {
      version           Version,
      modulus           INTEGER,  -- n
      publicExponent    INTEGER,  -- e
      privateExponent   INTEGER,  -- d
      prime1            INTEGER,  -- p
      prime2            INTEGER,  -- q
      exponent1         INTEGER,  -- d mod (p-1)
      exponent2         INTEGER,  -- d mod (q-1)
      coefficient       INTEGER,  -- (inverse of q) mod p
      otherPrimeInfos   OtherPrimeInfos OPTIONAL
  }


A sample private-key using the encoding and syntax above would look as follows:

-----BEGIN RSA PRIVATE KEY-----
MIGGAgEAAhkAr6M0MwwZb+PmNOex7pFe5IDLe+eKEhazAgMBAAECGBpkc9uX3dqq
bFVW224yqOR0m8LyV+x2wQINANs9bxnc7ZdljRmlHwINAM0WMid0p2sbmMOn7QIN
AMocs4yTOFFG5DJNHwIMOLmt76ndcMu2Sk/VAgwpTp5DBMk2FLZKfaY=
-----END RSA PRIVATE KEY-----


Final note: You've posted your private key online ... which means that you shouldn't use it anymore.