apxs has with VPATH builds (assumes source dir = build dir).
# Apache 1.3 shared module
libphp4.so: libmodphp4-so.a $(REGEX_LIB)
(cd sapi/apache; $(MAKE) mod_php4.o)
- $(APXS) $(INCLUDE) -c -o libphp4.so $(VERSION_SCRIPT) $(RPATHS) $(srcdir)/sapi/apache/mod_php4.c libmodphp4-so.a $(APXS_LDFLAGS) $(APXS_EXP)
+ $(APXS) $(INCLUDE) -c -o libphp4.so $(VERSION_SCRIPT) $(RPATHS) $(srcdir)/sapi/apache/mod_php4.o libmodphp4-so.a $(APXS_LDFLAGS) $(APXS_EXP)