Only run github actions on master branch.

.github/workflows/license_check.yml

diff --git a/.github/workflows/license_check.yml b/.github/workflows/license_check.yml
index ecc1281..5108c7e 100644
--- a/.github/workflows/license_check.yml
+++ b/.github/workflows/license_check.yml
@@ -1,6 +1,13 @@
 name: license check
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
 
 defaults:
   run:

.github/workflows/link_check.yml

diff --git a/.github/workflows/link_check.yml b/.github/workflows/link_check.yml
index acbd2e2..78de2eb 100644
--- a/.github/workflows/link_check.yml
+++ b/.github/workflows/link_check.yml
@@ -1,6 +1,13 @@
 name: link check
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
 
 defaults:
   run:

.github/workflows/os_x_mklbuild.yml

diff --git a/.github/workflows/os_x_mklbuild.yml b/.github/workflows/os_x_mklbuild.yml
index 70c9733..69ac3cf 100644
--- a/.github/workflows/os_x_mklbuild.yml
+++ b/.github/workflows/os_x_mklbuild.yml
@@ -1,6 +1,12 @@
 name: mkl continuous build
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
 
 jobs:
   macosx-x86_64:

.github/workflows/os_x_staticbuild.yml

diff --git a/.github/workflows/os_x_staticbuild.yml b/.github/workflows/os_x_staticbuild.yml
index 5502f93..4cbaf98 100644
--- a/.github/workflows/os_x_staticbuild.yml
+++ b/.github/workflows/os_x_staticbuild.yml
@@ -1,6 +1,13 @@
 name: continuous build
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - master
+  pull_request:
+    branches:
+    - master
+
 
 jobs:
   macosx-x86_64: