Fix: Fix linking to gpgme

Use pkg-config to search for gpgme linker flags. The gpgme-config tool
is deprecated and removed in a newer gpgme version. The gpgme package
comes already with a gpgme.pc file for pkg-config on Debian bullseye.

src/CMakeLists.txt

@@ -34,6 +34,7 @@ pkg_check_modules (GNUTLS REQUIRED gnutls>=3.2.15)
 pkg_check_modules (GLIB REQUIRED glib-2.0>=2.42)
 pkg_check_modules (LIBBSD REQUIRED libbsd)
 pkg_check_modules (LIBICAL REQUIRED libical>=1.00)
+pkg_check_modules (GPGME REQUIRED gpgme)
 
 message (STATUS "Looking for PostgreSQL...")
 find_program (PG_CONFIG_EXECUTABLE pg_config DOC "pg_config")
@@ -70,19 +71,22 @@ else (NOT XSLTPROC_EXECUTABLE)
  message (STATUS "Looking for xsltproc... ${XSLTPROC_EXECUTABLE}")
 endif (NOT XSLTPROC_EXECUTABLE)
 
-message (STATUS "Looking for gpgme...")
-find_library (GPGME gpgme)
-if (NOT GPGME)
- message (SEND_ERROR "The gpgme library is required.")
-else (NOT GPGME)
- message (STATUS "Looking for gpgme... ${GPGME}")
- execute_process (COMMAND gpgme-config --cflags
- OUTPUT_VARIABLE GPGME_CFLAGS
- OUTPUT_STRIP_TRAILING_WHITESPACE)
- execute_process (COMMAND gpgme-config --libs
- OUTPUT_VARIABLE GPGME_LDFLAGS
- OUTPUT_STRIP_TRAILING_WHITESPACE)
-endif (NOT GPGME)
+if (NOT GPGME_FOUND)
+ # fallback for older gpgme versions without gpgme.pc file
+ message (STATUS "Looking for gpgme...")
+ find_library (GPGME gpgme)
+ if (NOT GPGME)
+ message (SEND_ERROR "The gpgme library is required.")
+ else (NOT GPGME)
+ message (STATUS "Looking for gpgme... ${GPGME}")
+ execute_process (COMMAND gpgme-config --cflags
+ OUTPUT_VARIABLE GPGME_CFLAGS
+ OUTPUT_STRIP_TRAILING_WHITESPACE)
+ execute_process (COMMAND gpgme-config --libs
+ OUTPUT_VARIABLE GPGME_LDFLAGS
+ OUTPUT_STRIP_TRAILING_WHITESPACE)
+ endif (NOT GPGME)
+endif (NOT GPGME_FOUND)
 
 if (WITH_LIBTHEIA)
  find_package(Theia 1.0.0 REQUIRED)