Add IMOD/4.12.50-beta

Beta versions come from a different URL

EM/IMOD/build

@@ -1,4 +1,5 @@
 #!/usr/bin/env modbuild
+set -e
 
 pbuild::add_to_group 'EM'
 
@@ -7,6 +8,11 @@ pbuild::prep() {
     : ${CUDA_VERSION:?No CUDA_VERSION set}
     local cuda="${CUDA_VERSION%.*}"
     local filename="imod_${V_PKG}_RHEL7-64_CUDA${cuda}.sh"
+    if [[ $V_RELEASE == *beta* ]]; then
+        local url="https://bio3d.colorado.edu/ftp/latestIMOD/RHEL7-64_CUDA${cuda}/$filename"
+    else
+        local url="https://bio3d.colorado.edu/imod/AMD64-RHEL5/$filename"
+    fi
     local dst="$PMODULES_DISTFILESDIR/${filename}"
     if [ -f "$dst" ]; then
         echo "Found cached $dst" >&2
@@ -15,7 +21,7 @@ pbuild::prep() {
             --location \
             --fail \
             --output "$dst" \
-            "https://bio3d.colorado.edu/imod/AMD64-RHEL5/$filename"
+            "$url"
     fi
     }
 

EM/IMOD/files/variants

@@ -1,2 +1,3 @@
 IMOD/4.9.5	stable	
 IMOD/4.11.20	stable	cuda/10.1.105
+IMOD/4.12.50-beta	unstable	cuda/10.1.105