*-wrapper; Switch from infixSalt to suffixSalt

I hate the thing too even though I made it, and rather just get rid of
it. But we can't do that yet. In the meantime, this brings us more
inline with autoconf and will make it slightly easier for me to write a
pkg-config wrapper, which we need.

pkgs/build-support/setup-hooks/role.bash

@@ -3,21 +3,17 @@
 # derivation) in which the derivation is used.
 #
 # The role is intened to be use as part of other variables names like
-#  - $NIX_${role_pre}_SOMETHING
-#  - $NIX_SOMETHING_${role_post}
+#  - $NIX_SOMETHING${role_post}
 
 function getRole() {
     case $1 in
         -1)
-            role_pre='BUILD_'
             role_post='_FOR_BUILD'
             ;;
         0)
-            role_pre=''
             role_post=''
             ;;
         1)
-            role_pre='TARGET_'
             role_post='_FOR_TARGET'
             ;;
         *)
@@ -54,18 +50,18 @@ function getTargetRoleEnvHook() {
 }
 
 # This variant is inteneded specifically for code-prodocing tool wrapper scripts
-# `NIX_@wrapperName@_@infixSalt@_TARGET_*` tracks this (needs to be an exported
+# `NIX_@wrapperName@_TARGET_*_@suffixSalt@` tracks this (needs to be an exported
 # env var so can't use fancier data structures).
 function getTargetRoleWrapper() {
     case $targetOffset in
         -1)
-            export NIX_@wrapperName@_@infixSalt@_TARGET_BUILD=1
+            export NIX_@wrapperName@_TARGET_BUILD_@suffixSalt@=1
             ;;
         0)
-            export NIX_@wrapperName@_@infixSalt@_TARGET_HOST=1
+            export NIX_@wrapperName@_TARGET_HOST_@suffixSalt@=1
             ;;
         1)
-            export NIX_@wrapperName@_@infixSalt@_TARGET_TARGET=1
+            export NIX_@wrapperName@_TARGET_TARGET_@suffixSalt@=1
             ;;
         *)
             echo "@name@: used as improper sort of dependency" >2