I have a non-recursive Makefile.am with something like the following:
SHARED_SRCS = src/bar.cpp src/baz.cpp
bin_PROGRAMS = foo
foo_SOURCES = src/main.cpp $(SHARED_SRCS)
foo_CXXFLAGS = -I$(srcdir)/src $(SOME_CFLAGS)
foo_LDADD = $(SOME_LIBS)
check_PROGRAMS = test1 test2 test3
TESTS = test1 test2 test3
test1_SOURCES = tests/test1.cpp $(SHARED_SRCS)
test2_SOURCES = tests/test2.cpp $(SHARED_SRCS)
test3_SOURCES = tests/test3.cpp $(SHARED_SRCS)
test1_CXXFLAGS = $(foo_CXXFLAGS)
test2_CXXFLAGS = $(foo_CXXFLAGS)
test3_CXXFLAGS = $(foo_CXXFLAGS)
test1_LDADD = $(foo_LDADD)
test2_LDADD = $(foo_LDADD)
test3_LDADD = $(foo_LDADD)
However, every target builds its own SHARED_SRCS, getting them built 4 times, even when sharing the same flags.
Is there a way to get them built without creating a convenience library, e.g. libbar.a or libtool's libbar.la?
No, there's not. The point is that you're not rebuilding the sources, you're rebuilding binaries.
What you can do is build an intermediate .o consisting only of the shared sources, and then use that in your tests, and binaries.