'--verify-update', shasum support, OpenPGP signatures verification

src/openpgp/CMakeLists.txt

@@ -0,0 +1,18 @@
+file(GLOB_RECURSE SOURCES *.cpp)
+file(GLOB_RECURSE HEADERS *.h)
+
+find_library(GCRYPT_LIBRARY gcrypt)
+find_library(GPG_ERROR_LIBRARY gpg-error)
+
+add_library(openpgp
+  ${SOURCES}
+  ${HEADERS})
+
+target_include_directories(openpgp
+  PUBLIC
+    ${CMAKE_SOURCE_DIR}/monero/contrib/epee/include)
+
+target_link_libraries(openpgp
+  PUBLIC
+    ${GCRYPT_LIBRARY}
+    ${GPG_ERROR_LIBRARY})