package/qpdf: requires RC4 support in openssl

Fix the following build failure raised since bump to version 10.5.0 in
commit b5352c2177011ca389cbb7c68e78447549cbdaaa:

libqpdf/QPDFCrypto_openssl.cc: In constructor 'QPDFCrypto_openssl::QPDFCrypto_openssl()':
libqpdf/QPDFCrypto_openssl.cc:46:9: error: 'EVP_rc4' was not declared in this scope
   46 |     rc4(EVP_rc4()),
      |         ^~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/3b7f19ecb3303c9c9eb89c493c7e0d8a47b4be95

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/qpdf/Config.in

@@ -4,6 +4,7 @@ config BR2_PACKAGE_QPDF
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_5 # C++14
 	select BR2_PACKAGE_ZLIB
 	select BR2_PACKAGE_JPEG
+	select BR2_PACKAGE_LIBOPENSSL_ENABLE_RC4 if BR2_PACKAGE_LIBOPENSSL
 	help
 	  QPDF is a command-line program that does structural,
 	  content- preserving transformations on PDF files. It could