feat(autotools): basic usage

src/Makefile.am

@@ -0,0 +1,25 @@
+# define the subdirectories
+SUBDIRS = \
+	  ast \
+      parser \
+	  lexer \
+	  io_backend \
+	  execution \
+	  expansion
+#  + utils if needed
+
+bin_PROGRAMS = 42sh
+
+42sh_SOURCES = 42sh.c
+
+42sh_CPPFLAGS = -I%D%
+
+42sh_CFLAGS = -std=c99 -pedantic -Werror -Wall -Wextra -Wvla
+
+42sh_LDADD =  \
+       ast/libast.a \
+       parser/libparser.a \
+	   lexer/liblexer.a \
+	   io_backend/libio_backend.a \
+	   expansion/libexpansion.a \
+	   execution/libexecution.a