build: remove mingw linker workaround from win gitian descriptor

This workaround was added as part of the switch to gitian building using Ubuntu 14.04 (#6900).
However, it should no longer be required, as we have switched to Bionic (#13171), and that
has a far newer version of binutils.

binutils patch: https://sourceware.org/bugzilla/show_bug.cgi?id=16192

contrib/gitian-descriptors/gitian-win.yml

@@ -73,18 +73,10 @@ script: |
   done
   }
 
-  function create_per-host_linker_wrapper {
-  # This is only needed for trusty, as the mingw linker leaks a few bytes of
-  # heap, causing non-determinism. See discussion in https://github.com/bitcoin/bitcoin/pull/6900
+  function create_per-host_compiler_wrapper {
+  # -posix variant is required for c++11 threading.
   for i in $HOSTS; do
     mkdir -p ${WRAP_DIR}/${i}
-    for prog in collect2; do
-        echo '#!/usr/bin/env bash' > ${WRAP_DIR}/${i}/${prog}
-        REAL=$(${i}-gcc -print-prog-name=${prog})
-        echo "export MALLOC_PERTURB_=255" >> ${WRAP_DIR}/${i}/${prog}
-        echo "${REAL} \$@" >> $WRAP_DIR/${i}/${prog}
-        chmod +x ${WRAP_DIR}/${i}/${prog}
-    done
     for prog in gcc g++; do
         echo '#!/usr/bin/env bash' > ${WRAP_DIR}/${i}-${prog}
         echo "REAL=\`which -a ${i}-${prog}-posix | grep -v ${WRAP_DIR}/${i}-${prog} | head -1\`" >> ${WRAP_DIR}/${i}-${prog}
@@ -101,7 +93,7 @@ script: |
   export PATH_orig=${PATH}
   create_global_faketime_wrappers "2000-01-01 12:00:00"
   create_per-host_faketime_wrappers "2000-01-01 12:00:00"
-  create_per-host_linker_wrapper "2000-01-01 12:00:00"
+  create_per-host_compiler_wrapper "2000-01-01 12:00:00"
   export PATH=${WRAP_DIR}:${PATH}
 
   cd bitcoin
@@ -115,7 +107,7 @@ script: |
   export PATH=${PATH_orig}
   create_global_faketime_wrappers "${REFERENCE_DATETIME}"
   create_per-host_faketime_wrappers "${REFERENCE_DATETIME}"
-  create_per-host_linker_wrapper "${REFERENCE_DATETIME}"
+  create_per-host_compiler_wrapper "${REFERENCE_DATETIME}"
   export PATH=${WRAP_DIR}:${PATH}
 
   # Create the release tarball using (arbitrarily) the first host