This has been broken for the last few days:
libtool: link: ( cd ".libs" && rm -f "lib10_quota_plugin.la" && ln -s
"../lib10_quota_plugin.la" "lib10_quota_plugin.la" )
libtool: link: x86_64-pc-linux-gnu-gcc -std=gnu99 -O2 -pipe
-march=native -mtune=native -Wall -W -Wmissing-prototypes
-Wmissing-declarations -Wpointer-arith -Wchar-subscripts -Wformat=2
-Wbad-function-cast -fno-builtin-strftime -Wstrict-aliasing=2 -Wl,-O1 -o
.libs/quota-status quota-status.o .libs/quota.o .libs/quota-count.o
.libs/quota-fs.o .libs/quota-dict.o .libs/quota-dirsize.o
.libs/quota-imapc.o .libs/quota-maildir.o .libs/quota-plugin.o
.libs/quota-storage.o .libs/quota-util.o .libs/rquota_xdr.o
-Wl,--export-dynamic -Wl,--as-needed
../../../src/lib-storage/.libs/libdovecot-storage.so
/var/tmp/portage/net-mail/dovecot-9999_p20170427/work/dovecot-9999_p20170427/src/lib-dovecot/.libs/libdovecot.so
../../../src/lib-imap-storage/.libs/libimap-storage.a
../../../src/lib-dovecot/.libs/libdovecot.so -ldl -Wl,-rpath
-Wl,/usr/lib64/dovecot
.libs/quota-imapc.o: In function imapc_quota_refresh': quota-imapc.c:(.text+0x8dd): undefined reference to imapc_storage_client_register_untagged'
quota-imapc.c:(.text+0x8f7): undefined reference to
imapc_storage_client_register_untagged' quota-imapc.c:(.text+0x90a): undefined reference to imapc_client_get_capabilities'
quota-imapc.c:(.text+0x964): undefined reference to
imapc_simple_context_init' quota-imapc.c:(.text+0x975): undefined reference to imapc_simple_callback'
quota-imapc.c:(.text+0x97e): undefined reference to imapc_client_cmd' quota-imapc.c:(.text+0x996): undefined reference to imapc_command_sendf'
quota-imapc.c:(.text+0x99e): undefined reference to imapc_simple_run' quota-imapc.c:(.text+0xaab): undefined reference to imapc_simple_context_init'
quota-imapc.c:(.text+0xabc): undefined reference to imapc_simple_callback' quota-imapc.c:(.text+0xac5): undefined reference to imapc_client_cmd'
quota-imapc.c:(.text+0xadd): undefined reference to imapc_command_sendf' quota-imapc.c:(.text+0xae5): undefined reference to imapc_simple_run'
collect2: error: ld returned 1 exit status
make[4]: *** [Makefile:694: quota-status] Error 1
make[4]: Leaving directory
'/var/tmp/portage/net-mail/dovecot-9999_p20170427/work/dovecot-9999_p20170427/src/plugins/quota'