autoconf: make -k Status

1 
1 12.17 Exit Status of `make -k'
1 ==============================
1 
1 Do not rely on the exit status of `make -k'.  Some implementations
1 reflect whether they encountered an error in their exit status; other
1 implementations always succeed.
1 
1      $ cat Makefile
1      all:
1              false
1      $ make -k; echo exit status: $?    # GNU make
1      false
1      make: *** [all] Error 1
1      exit status: 2
1      $ pmake -k; echo exit status: $?   # BSD make
1      false
1      *** Error code 1 (continuing)
1      exit status: 0
1