Hack: Attempt to make Nim building to work by moving config.nims out

This should get me around the issue reported in
nim-lang/Nim#15843.

> /home/travis/build/kaushalmodi/hello_musl/nim/4c19c5dfae01638ae66fc2c1561762d94fb36a1a/lib/pure/fenv.nim(17,
3) Error: cannot 'importc' variable at compile time; FE_DIVBYZERO

.travis.yml

@@ -49,6 +49,12 @@ install:
   - |
     if [[ ! -f "${NIMDIR}/bin/nim" ]]
     then
+      # If the git repo contains a config.nims, temporarily move it, else it fails the
+      # building of koch.
+      if [[ -f "${TRAVIS_BUILD_DIR}/config.nims" ]]
+      then
+        mv "${TRAVIS_BUILD_DIR}/config.nims" "${TRAVIS_BUILD_DIR}/config.nims.bkp"
+      fi
       rm -rf nim
       mkdir -p nim
       git clone --single-branch --branch devel --depth=1 "${NIMREPO}" "${NIMDIR}"
@@ -61,6 +67,11 @@ install:
       ./koch boot -d:release
       # After building nim, wipe csources to save on cache space.
       rm -rf csources
+      # Restore the backed up config.nims if present.
+      if [[ -f "${TRAVIS_BUILD_DIR}/config.nims.bkp" ]]
+      then
+        mv "${TRAVIS_BUILD_DIR}/config.nims.bkp" "${TRAVIS_BUILD_DIR}/config.nims"
+      fi
     fi
   # - |
   #   if [[ ! -f "${NIMDIR}/bin/nimble" ]]