agent/Makefile.am: Rename agent binary

Guile is confused by agent.scm and agent.  It will try to load the ELF file
instead of the Scheme script when `(use-modules (agent))`.

Change-Id: Ieead4c384f10df9ead351a6ae66b21f708e97424

test/agent/Makefile.am

@@ -3,9 +3,9 @@ include $(top_srcdir)/globals.mk
 AM_CXXFLAGS += -I$(top_srcdir)/src -I./src $(GUILE_CFLAGS) -rdynamic
 AM_LDFLAGS  += $(GUILE_LIBS)
 
-noinst_PROGRAMS = agent
+noinst_PROGRAMS = agent.exe
 
-agent_SOURCES =                   \
+agent_exe_SOURCES =               \
 	src/main.cpp              \
 	src/utils.h               \
 	src/bindings/bindings.cpp \
@@ -15,4 +15,4 @@ agent_SOURCES =                   \
 	src/bindings/signal.cpp   \
 	src/bindings/signal.h
 
-agent_LDADD = $(top_builddir)/src/libring.la
+agent_exe_LDADD = $(top_builddir)/src/libring.la