Broken, again, by yours truly in
bc11759dd1fd ("build: switch to
hiding libnotmuch symbols by default"). Reference notmuch.sym via
$(srctree).
LINKER_NAME = libnotmuch.$(LIBRARY_SUFFIX)
SONAME = $(LINKER_NAME).$(LIBNOTMUCH_VERSION_MAJOR)
LIBNAME = $(SONAME).$(LIBNOTMUCH_VERSION_MINOR).$(LIBNOTMUCH_VERSION_RELEASE)
-LIBRARY_LINK_FLAG = -shared -Wl,--version-script=$(lib)/notmuch.sym,-soname=$(SONAME) $(NO_UNDEFINED_LDFLAGS)
+LIBRARY_LINK_FLAG = -shared -Wl,--version-script=$(srcdir)/$(lib)/notmuch.sym,-soname=$(SONAME) $(NO_UNDEFINED_LDFLAGS)
ifeq ($(PLATFORM),OPENBSD)
LIBRARY_LINK_FLAG += -lc
endif