Renable parallel build again.

Now that we have zero diff on non-parallel builds, let see if adding
parallelism breaks it.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>

open_pdks/build-open_pdks.sh

diff --git a/open_pdks/build-open_pdks.sh b/open_pdks/build-open_pdks.sh
index 3645d95..a3bdccd 100755
--- a/open_pdks/build-open_pdks.sh
+++ b/open_pdks/build-open_pdks.sh
@@ -91,8 +91,7 @@
         $QFLOW \
         $XSCHEM \
 
-  #make -j$(nproc) | tee /host/out/pdk-$TTOOL.build.log
-  make -j1 | tee /host/out/pdk-$TTOOL.build.log
+  make -j$(nproc) | tee /host/out/pdk-$TTOOL.build.log
   make DESTDIR=/host/out/pdk-$TTOOL install | tee /host/out/pdk-$TTOOL.install.log
   echo "========================================="