Clone the VPP repository and hack the vagrant bootstrap script to put them into /vpp (adding 'vpp1.vm.synced_folder "<where-your-vpp-sources-are>", "/vpp", disabled: false' line into vagrant-demo/Vagrantfile below similar line that mentions honeycomb is not sufficient because it will cause the build in VMs running under Vagrant For Windows to fail with "Protocol error"), then do "vagrant up". Assuming the sources were correctly placed into /vpp by the hack, you will get the following error during the VPP build:

Making all in java
==> vpp1: make[3]: Entering directory `/vpp/build-root/build-vpp_debug-native/vpp-api/java'
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppVersion.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppVersion ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppInterfaceDetails.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppInterfaceDetails ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppInterfaceCounters.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppInterfaceCounters ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppBridgeDomainInterfaceDetails.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppBridgeDomainInterfaceDetails ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppBridgeDomainDetails.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppBridgeDomainDetails ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppL2Fib.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppL2Fib ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppIPv4Address.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppIPv4Address ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppIPv6Address.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppIPv6Address ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppVxlanTunnelDetails.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppVxlanTunnelDetails ; \
==> vpp1: javac -classpath . -d . /vpp/build-data/../vpp-api/java/japi/org/openvpp/vppjapi/vppConn.java ; \
==> vpp1: /usr/bin/javah -classpath . -d japi org.openvpp.vppjapi.vppConn ;
==> vpp1: jVpp API
==> vpp1: Python bindings written to defs_vpp_papi.py
==> vpp1: Generating DTOs
==> vpp1: Generating JVpp
==> vpp1: Generating Callback interfaces
==> vpp1: Generating jvpp C
==> vpp1: Generating JVpp future facade
==> vpp1: Generating JVpp callback facade
==> vpp1: jvpp/gen/target/org/openvpp/jvpp/test/CallbackJVppFacadeTest.java:31: error: illegal start of expression
==> vpp1: private static ShowVersionCallback showVersionCallback1 = msg ->
==> vpp1: ^
==> vpp1: jvpp/gen/target/org/openvpp/jvpp/test/CallbackJVppFacadeTest.java:36: error: illegal start of expression
==> vpp1: private static ShowVersionCallback showVersionCallback2 = msg ->
==> vpp1: ^
==> vpp1: 2 errors
==> vpp1: JVpp compilation failed: 1
==> vpp1: Error: Could not find class file for 'org.openvpp.jvpp.VppJNIConnection'.
==> vpp1: Error: Could not find class file for 'org.openvpp.jvpp.JVppImpl'.
==> vpp1: make[3]:
==> vpp1: *** [jvpp/org_openvpp_jvpp_VppJNIConnection.h] Error 1
==> vpp1: make[3]:
==> vpp1: *** Waiting for unfinished jobs....
==> vpp1: make[3]: Leaving directory `/vpp/build-root/build-vpp_debug-native/vpp-api/java'
==> vpp1: make[2]:
==> vpp1: *** [all-recursive] Error 1
==> vpp1: make[2]: Leaving directory `/vpp/build-root/build-vpp_debug-native/vpp-api'
==> vpp1: make[1]:
==> vpp1: *** [vpp-api-build] Error 2
==> vpp1: make[1]: Leaving directory `/vpp/build-root'
==> vpp1: make:
==> vpp1: *** [install-deb] Error 1