configure: Don't hard-code strip tool

For reasons that I don't entirely understand we didn't previously detect
`strip` using autoconf. This naturally broke during cross-compilation.
How did this ever work? I have no idea.

Test Plan: Try cross-compiling

Reviewers: austin, hvr, angerman

Subscribers: rwbarton, thomie, erikd

Differential Revision: https://phabricator.haskell.org/D4008

configure.ac

@@ -605,6 +605,13 @@ fi
 RanlibCmd="$RANLIB"
 RANLIB="$RanlibCmd"
 
+dnl ** which strip to use?
+dnl --------------------------------------------------------------
+AC_CHECK_TARGET_TOOL([STRIP], [strip])
+StripCmd="$STRIP"
+AC_SUBST([StripCmd])
+
+
 dnl ** which libtool to use?
 dnl --------------------------------------------------------------
 # The host normalization on Windows breaks autoconf, it no longer

distrib/configure.ac.in

@@ -178,6 +178,12 @@ dnl ** how to invoke `ar' and `ranlib'
 FP_PROG_AR_SUPPORTS_ATFILE
 FP_PROG_AR_NEEDS_RANLIB
 
+dnl ** which strip to use?
+dnl --------------------------------------------------------------
+AC_CHECK_TARGET_TOOL([STRIP], [strip])
+StripCmd="$STRIP"
+AC_SUBST([StripCmd])
+
 dnl ** Have libdw?
 dnl --------------------------------------------------------------
 dnl Check for a usable version of libdw/elfutils

mk/config.mk.in

@@ -775,7 +775,7 @@ else ifeq "$(TARGETPLATFORM)" "arm-unknown-linux"
 # The hack of using `:` to disable stripping is implemented by ghc-cabal.
 STRIP_CMD      = :
 else
-STRIP_CMD      = strip
+STRIP_CMD      = @StripCmd@
 endif
 PATCH_CMD      = @PatchCmd@
 TAR_CMD        = @TarCmd@