Try removing ldap.h header

Author: nikic

azure/apt.yml

@@ -59,5 +59,7 @@ steps:
       wget https://download.oracle.com/otn_software/linux/instantclient/instantclient-sdk-linuxx64.zip
       unzip instantclient-sdk-linuxx64.zip
       mv instantclient_*_* /opt/oracle/instantclient
+      # Interferes with libldap2 headers.
+      rm /opt/oracle/instantclient/sdk/include/ldap.h
       echo "##vso[task.setvariable variable=LD_LIBRARY_PATH]/opt/oracle/instantclient:$LD_LIBRARY_PATH"
     displayName: 'Install Oracle Instant Client'