pkcs7: provide fuzz harness

This allows for pkcs7 fuzz testing with OSS-Fuzz.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
diff --git a/programs/fuzz/CMakeLists.txt b/programs/fuzz/CMakeLists.txt
index c7fcd35..7747744 100644
--- a/programs/fuzz/CMakeLists.txt
+++ b/programs/fuzz/CMakeLists.txt
@@ -12,6 +12,7 @@
     fuzz_x509crl
     fuzz_x509crt
     fuzz_x509csr
+    fuzz_pkcs7
 )
 
 set(executables_with_common_c