Makefile: autobuild dependency rules

This uses gcc to generate dependency rules for each `.o` file, based on the
corresponding `.c` file, into a new set of `.d` files (which are also defined
to depend on the same set of source files as their `.o` files).

Result:
* all objectfile dependencies are correctly calculated
* only the necessary dependencies are recalculated when a sourcefile is updated

Inspiration for the build rules:
* http://www.gnu.org/software/make/manual/make.html#Automatic-Prerequisites
* http://make.paulandlesley.org/autodep.html

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index aa36ff7..1e016e5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,3 +3,4 @@ cgit
 cgit.conf
 VERSION
 *.o
+*.d