bring back std/ prefix within compiler and ensure it works in bootstrap + bsd (#17902)

* [WIP] bring back std/ prefix within compiler and ensure it works in bootstrap + bsd

* refs https://github.com/nim-lang/Nim/pull/16282#discussion_r616846863
* sounds very similar to https://github.com/nim-lang/Nim/pull/14291
* more: vmops
* update tools/ci_generate.nim
* auto-generate freebsd.yml as well, to avoid duplication with openbsd.yml
* cleanup
* undo temporary CI removal

.builds/freebsd.yml

@@ -1,3 +1,5 @@
+## DO NO EDIT DIRECTLY! auto-generated by `nim r tools/ci_generate.nim`
+
 # see https://man.sr.ht/builds.sr.ht/compatibility.md#freebsd
 image: freebsd/latest
 packages:
@@ -8,9 +10,12 @@ packages:
 - devel/sfml
 - www/node
 - devel/gmake
+
+
 sources:
 - https://github.com/nim-lang/Nim
 environment:
+  NIM_TESTAMENT_BATCH: "0_1"
   CC: /usr/bin/clang
 tasks:
 - setup: |
@@ -20,9 +25,10 @@ tasks:
     $nim_csources c --skipUserCfg --skipParentCfg koch
     echo 'export PATH=$HOME/Nim/bin:$PATH' >> $HOME/.buildenv
 - test: |
+    set -e
     cd Nim
     if ! ./koch runCI; then
-      nim c -r tools/ci_testresults.nim
+      nim r tools/ci_testresults.nim
       exit 1
     fi
 triggers: