Use build_all.sh for building nim devel

Fixes nim-lang/Nim#15843 .

.travis.yml

@@ -22,20 +22,15 @@ install:
       mkdir -p nim
       git clone --single-branch --branch devel --depth=1 "${NIMREPO}" "${NIMDIR}"
       cd "${NIMDIR}" || exit
-      [ -d csources ] || git clone --depth 1 https://github.com/nim-lang/csources.git
-      cd csources
-      sh build.sh
-      cd ..
-      ./bin/nim c koch
-      ./koch boot -d:release
-      # After building nim, wipe csources to save on cache space.
-      rm -rf csources
+      # Don't build 'koch tools'; remove that line from build_all.sh.
+      sed -i '/koch tools/d' build_all.sh
+      sh build_all.sh # https://github.com/nim-lang/Nim/issues/17907#issuecomment-831654235
     fi
   - |
     if [[ ! -f "${NIMDIR}/bin/nimble" ]]
     then
       cd "${NIMDIR}" || exit
-      ./koch nimble
+      ./koch nimble --skipUserCfg --skipParentCfg
     fi
   - export PATH="${NIMDIR}/bin:${PATH}"
   - nim -v