[CI] now enables runs NIM_COMPILE_TO_CPP=true without allow_failures

.travis.yml

@@ -14,8 +14,9 @@ matrix:
     - os: osx
       env: NIM_COMPILE_TO_CPP=true
 
-  allow_failures:
-    - env: NIM_COMPILE_TO_CPP=true
+# To allow failures for a failing configuration, use something like:
+#  allow_failures:
+#    - env: NIM_COMPILE_TO_CPP=true
 #    - os: osx
 
 addons:

koch.nim

@@ -281,7 +281,8 @@ proc boot(args: string) =
   let smartNimcache = (if "release" in args: "nimcache/r_" else: "nimcache/d_") &
                       hostOs & "_" & hostCpu
 
-  copyExe(findStartNim(), 0.thVersion)
+  let nimStart = findStartNim()
+  copyExe(nimStart, 0.thVersion)
   for i in 0..2:
     let defaultCommand = if useCpp: "cpp" else: "c"
     let bootOptions = if args.len == 0 or args.startsWith("-"): defaultCommand else: ""
@@ -292,7 +293,11 @@ proc boot(args: string) =
         # Note(D20190115T162028:here): the configs are skipped for bootstrap
         # (1st iteration) to prevent newer flags from breaking bootstrap phase.
         # fixes #10030.
-      extraOption.add " -d:nimBoostrapCsources0_19_0"
+      let ret = execCmdEx(nimStart & " --version")
+      doAssert ret.exitCode == 0
+      let version = ret.output.splitLines[0]
+      if version.startsWith "Nim Compiler Version 0.19.0":
+        extraOption.add " -d:nimBoostrapCsources0_19_0"
         # remove this when csources get updated
     exec i.thVersion & " $# $# $# --nimcache:$# compiler" / "nim.nim" %
       [bootOptions, extraOption, args, smartNimcache]