autoconf: obj/ and Make

1 
1 12.16 The `obj/' Subdirectory and Make
1 ======================================
1 
1 Never name one of your subdirectories `obj/' if you don't like
1 surprises.
1 
1    If an `obj/' directory exists, BSD `make' enters it before reading
1 the makefile.  Hence the makefile in the current directory is not read.
1 
1      $ cat Makefile
1      all:
1              echo Hello
1      $ cat obj/Makefile
1      all:
1              echo World
1      $ make      # GNU make
1      echo Hello
1      Hello
1      $ pmake     # BSD make
1      echo World
1      World
1