Fix platform detection in bindists

In a bindist, we generate files like the hsc2hs wrapper.
This means we need to have the right values for the variables like
CONF_GCC_LINKER_OPTS_STAGE1 which in turn means we need to know what
platform we're on.

aclocal.m4

@@ -4,6 +4,83 @@
 # ensure we don't clash with any pre-supplied autoconf ones.
 
 
+# FPTOOLS_SET_PLATFORM_VARS
+# ----------------------------------
+# Set the platform variables
+AC_DEFUN([FPTOOLS_SET_PLATFORM_VARS],
+[
+    # If no argument was given for a configuration variable, then discard
+    # the guessed canonical system and use the configuration of the
+    # bootstrapping ghc. If an argument was given, map it from gnu format
+    # to ghc format.
+    #
+    # For why we do it this way, see: #3637, #1717, #2951
+    #
+    # In bindists, we haven't called AC_CANONICAL_{BUILD,HOST,TARGET}
+    # so this justs uses $bootstrap_target.
+
+    if test "$build_alias" = ""
+    then
+        if test "$bootstrap_target" != ""
+        then
+            build=$bootstrap_target
+            echo "Build platform inferred as: $build"
+        else
+            echo "Can't work out build platform"
+            exit 1
+        fi
+
+        BuildArch=`echo "$build" | sed 's/-.*//'`
+        BuildVendor=`echo "$build" | sed -e 's/.*-\(.*\)-.*/\1/'`
+        BuildOS=`echo "$build" | sed 's/.*-//'`
+    else
+        GHC_CONVERT_CPU([$build_cpu], [BuildArch])
+        GHC_CONVERT_VENDOR([$build_vendor], [BuildVendor])
+        GHC_CONVERT_OS([$build_os], [BuildOS])
+    fi
+
+    if test "$host_alias" = ""
+    then
+        if test "$bootstrap_target" != ""
+        then
+            host=$bootstrap_target
+            echo "Host platform inferred as: $host"
+        else
+            echo "Can't work out host platform"
+            exit 1
+        fi
+
+        HostArch=`echo "$host" | sed 's/-.*//'`
+        HostVendor=`echo "$host" | sed -e 's/.*-\(.*\)-.*/\1/'`
+        HostOS=`echo "$host" | sed 's/.*-//'`
+    else
+        GHC_CONVERT_CPU([$host_cpu], [HostArch])
+        GHC_CONVERT_VENDOR([$host_vendor], [HostVendor])
+        GHC_CONVERT_OS([$host_os], [HostOS])
+    fi
+
+    if test "$target_alias" = ""
+    then
+        if test "$bootstrap_target" != ""
+        then
+            target=$bootstrap_target
+            echo "Target platform inferred as: $target"
+        else
+            echo "Can't work out target platform"
+            exit 1
+        fi
+
+        TargetArch=`echo "$target" | sed 's/-.*//'`
+        TargetVendor=`echo "$target" | sed -e 's/.*-\(.*\)-.*/\1/'`
+        TargetOS=`echo "$target" | sed 's/.*-//'`
+    else
+        GHC_CONVERT_CPU([$target_cpu], [TargetArch])
+        GHC_CONVERT_VENDOR([$target_vendor], [TargetVendor])
+        GHC_CONVERT_OS([$target_os], [TargetOS])
+    fi
+])
+
+
 # FPTOOLS_SET_C_LD_FLAGS
 # ----------------------------------
 # Set the C, LD and CPP flags for a given platform

configure.ac

@@ -200,72 +200,7 @@ AC_CANONICAL_BUILD
 AC_CANONICAL_HOST
 AC_CANONICAL_TARGET
 
-# If no argument was given for a configuration variable, then discard
-# the guessed canonical system and use the configuration of the
-# bootstrapping ghc. If an argument was given, map it from gnu format
-# to ghc format.
-#
-# For why we do it this way, see: #3637, #1717, #2951
-
-if test "$build_alias" = ""
-then
-    if test "${WithGhc}" != ""
-    then
-        build=$bootstrap_target
-        echo "Build platform inferred as: $build"
-    else
-        echo "Can't work out build platform"
-        exit 1
-    fi
-
-    BuildArch=`echo "$build" | sed 's/-.*//'`
-    BuildVendor=`echo "$build" | sed -e 's/.*-\(.*\)-.*/\1/'`
-    BuildOS=`echo "$build" | sed 's/.*-//'`
-else
-    GHC_CONVERT_CPU([$build_cpu], [BuildArch])
-    GHC_CONVERT_VENDOR([$build_vendor], [BuildVendor])
-    GHC_CONVERT_OS([$build_os], [BuildOS])
-fi
-
-if test "$host_alias" = ""
-then
-    if test "${WithGhc}" != ""
-    then
-        host=$bootstrap_target
-        echo "Host platform inferred as: $host"
-    else
-        echo "Can't work out host platform"
-        exit 1
-    fi
-
-    HostArch=`echo "$host" | sed 's/-.*//'`
-    HostVendor=`echo "$host" | sed -e 's/.*-\(.*\)-.*/\1/'`
-    HostOS=`echo "$host" | sed 's/.*-//'`
-else
-    GHC_CONVERT_CPU([$host_cpu], [HostArch])
-    GHC_CONVERT_VENDOR([$host_vendor], [HostVendor])
-    GHC_CONVERT_OS([$host_os], [HostOS])
-fi
-
-if test "$target_alias" = ""
-then
-    if test "${WithGhc}" != ""
-    then
-        target=$bootstrap_target
-        echo "Target platform inferred as: $target"
-    else
-        echo "Can't work out target platform"
-        exit 1
-    fi
-
-    TargetArch=`echo "$target" | sed 's/-.*//'`
-    TargetVendor=`echo "$target" | sed -e 's/.*-\(.*\)-.*/\1/'`
-    TargetOS=`echo "$target" | sed 's/.*-//'`
-else
-    GHC_CONVERT_CPU([$target_cpu], [TargetArch])
-    GHC_CONVERT_VENDOR([$target_vendor], [TargetVendor])
-    GHC_CONVERT_OS([$target_os], [TargetOS])
-fi
+FPTOOLS_SET_PLATFORM_VARS
 
 exeext=''
 soext='.so'

distrib/configure.ac.in

@@ -18,6 +18,9 @@ dnl--------------------------------------------------------------------
 
 FP_GMP
 
+bootstrap_target=`ghc/stage2/build/tmp/ghc-stage2 +RTS --info | grep '^ ,("Target platform"' | sed -e 's/.*, "//' -e 's/")//' | tr -d '\r'`
+FPTOOLS_SET_PLATFORM_VARS
+
 #
 dnl ** Check Perl installation **
 #