build: Fix distcheck due to subdir sources

enlightenment_fm needs some files that are not in its subdirectory, but
rather are shared with enlightenment.

Possible solutions:

1) Use a non-recursive build for enlightenment_fm.
2) Factor out a convenience library containing necessary files
3) Copy over or link the files to build tree directory during build

For simplicity (3) is implemented here. Some files were not necessary
(e_prefix.c and e_sha1.c) and the others are now linked during build to
it's original location.

src/bin/e_fm/.gitignore

@@ -0,0 +1,4 @@
+/e_fm_shared_codec.c
+/e_fm_shared_device.c
+/e_user.c
+

src/bin/e_fm/Makefile.am

@@ -34,13 +34,17 @@ if HAVE_EEZE_MOUNT
 AM_CFLAGS += @EEZE_CFLAGS@ @EET_CFLAGS@
 LIBS += @EEZE_LIBS@ @EET_LIBS@
 eeze_s = \
-../e_prefix.c \
 e_fm_main_eeze.h \
 e_fm_main_eeze.c
 else
 eeze_s =
 endif
 
+shared_sources = \
+e_fm_shared_codec.c \
+e_fm_shared_device.c \
+e_user.c
+
 enlightenment_fm_SOURCES = \
 e_fm_main.h \
 e_fm_ipc.h \
@@ -48,9 +52,11 @@ e_fm_main.c \
 e_fm_ipc.c \
 $(udisks_s) \
 $(eeze_s) \
-../e_fm_shared_codec.c \
-../e_fm_shared_device.c \
-../e_user.c \
-../e_sha1.c
+$(shared_sources)
+
+$(shared_sources): %.c: $(abs_top_srcdir)/src/bin/%.c
+	$(AM_V_GEN) $(LN_S) -f $< $@
+
+CLEANFILES = $(shared_sources)
 
 enlightenment_fm_LDADD = @E_FM_LIBS@