Make nightly workflows not run on forks of openvdb/fvdb-core (#319)

Nightly workflows were running on my fork, but failing after 24 hours of
waiting because my fork can't get runners. This PR adds a check to
prevent the nightly workflow from running on a fork even if the fork has
actions enabled.

---------

Signed-off-by: Mark Harris <[email protected]>

Author: harrism

.github/workflows/cu128-nightly.yml

@@ -16,7 +16,7 @@ permissions:
 
 jobs:
   fvdb-build:
-    if: ${{ !startsWith(github.event.pull_request.title, 'Draft:') }}
+    if: ${{ github.repository == 'openvdb/fvdb-core' && !startsWith(github.event.pull_request.title, 'Draft:') }}
     name: fVDB Build
     runs-on:
       - self-hosted
@@ -160,6 +160,7 @@ jobs:
           echo "Cleanup completed"
 
   fvdb-benchmarks:
+    if: ${{ github.repository == 'openvdb/fvdb-core' }}
     needs: [fvdb-build]
     name: fVDB Continuous Benchmarking
     runs-on:

.github/workflows/cu130-nightly.yml

@@ -14,7 +14,7 @@ permissions:
 
 jobs:
   fvdb-build:
-    if: ${{ !startsWith(github.event.pull_request.title, 'Draft:') }}
+    if: ${{ github.repository == 'openvdb/fvdb-core' && !startsWith(github.event.pull_request.title, 'Draft:') }}
     name: fVDB Build
     runs-on:
       - self-hosted
@@ -158,6 +158,7 @@ jobs:
           echo "Cleanup completed"
 
   fvdb-benchmarks:
+    if: ${{ github.repository == 'openvdb/fvdb-core' }}
     needs: [fvdb-build]
     name: fVDB Continuous Benchmarking
     runs-on:

.github/workflows/nightly.yml

@@ -16,7 +16,7 @@ permissions:
 
 jobs:
   fvdb-build:
-    if: ${{ !startsWith(github.event.pull_request.title, 'Draft:') }}
+    if: ${{ github.repository == 'openvdb/fvdb-core' && !startsWith(github.event.pull_request.title, 'Draft:') }}
     name: fVDB Build
     runs-on:
       - self-hosted
@@ -133,6 +133,7 @@ jobs:
           echo "Cleanup completed"
 
   fvdb-benchmarks:
+    if: ${{ github.repository == 'openvdb/fvdb-core' }}
     needs: [fvdb-build]
     name: fVDB Continuous Benchmarking
     runs-on: