binutils-wrapper: Init

Factor a binutils wrapper out of cc-wrapper. While only LD is wrapped,
the setup hook defines environment variables on behalf of other
utilites.

pkgs/build-support/cc-wrapper/add-flags.sh

@@ -10,15 +10,8 @@ var_templates_list=(
     NIX+CXXSTDLIB_COMPILE
     NIX+CXXSTDLIB_LINK
     NIX+GNATFLAGS_COMPILE
-    NIX+IGNORE_LD_THROUGH_GCC
-    NIX+LDFLAGS
-    NIX+LDFLAGS_BEFORE
-    NIX+LDFLAGS_AFTER
 )
-
 var_templates_bool=(
-    NIX+SET_BUILD_ID
-    NIX+DONT_SET_RPATH
     NIX+ENFORCE_NO_NATIVE
 )
 
@@ -62,17 +55,13 @@ if [ -e @out@/nix-support/gnat-cflags ]; then
     NIX_@infixSalt@_GNATFLAGS_COMPILE="$(< @out@/nix-support/gnat-cflags) $NIX_@infixSalt@_GNATFLAGS_COMPILE"
 fi
 
-if [ -e @out@/nix-support/libc-ldflags ]; then
-    NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/libc-ldflags)"
-fi
-
 if [ -e @out@/nix-support/cc-ldflags ]; then
+    # We don't import this above, but just tack this on know. binutils-wrapper's
+    # add-flags will not clobber it.
+    #
+    # TODO(@Ericson2314): Consider `NIX_@infixSalt@_CFLAGS_LINK` instead
     NIX_@infixSalt@_LDFLAGS+=" $(< @out@/nix-support/cc-ldflags)"
 fi
 
-if [ -e @out@/nix-support/libc-ldflags-before ]; then
-    NIX_@infixSalt@_LDFLAGS_BEFORE="$(< @out@/nix-support/libc-ldflags-before) $NIX_@infixSalt@_LDFLAGS_BEFORE"
-fi
-
 # That way forked processes will not extend these environment variables again.
 export NIX_CC_WRAPPER_@infixSalt@_FLAGS_SET=1