fix(ci): Fix pipeline change to Ubuntu 18.04

.github/workflows/build-desktop.yml

@@ -44,7 +44,7 @@ jobs:
         sudo apt install -y gcc-multilib g++-multilib build-essential libssl-dev rpm libsecret-1-dev \
           software-properties-common apt-transport-https libudev-dev libusb-1.0-0-dev \
           llvm-dev libclang-dev clang
-      if: matrix.os == 'ubuntu-latest'
+      if: matrix.os == 'ubuntu-18.04'
 
     - name: Enable verbose output for electron-builder (macOS/Linux)
       run: echo "DEBUG=electron-builder" >> $GITHUB_ENV
@@ -84,12 +84,12 @@ jobs:
     - name: Build Electron app (Linux)
       run: yarn compile:linux
       working-directory: packages/desktop
-      if: matrix.os == 'ubuntu-latest'
+      if: matrix.os == 'ubuntu-18.04'
 
     - name: Compute checksums (Linux)
       run: for i in `ls | grep 'firefly-desktop*'` ; do sha256sum $i | awk {'print $1'} > $i.sha256 ; done
       working-directory: packages/desktop/out
-      if: matrix.os == 'ubuntu-latest'
+      if: matrix.os == 'ubuntu-18.04'
 
     - name: Compute checksums (macOS)
       run: for i in `ls | grep 'firefly-desktop*'` ; do shasum -a 256 $i | awk {'print $1'} > $i.sha256 ; done
@@ -139,7 +139,7 @@ jobs:
     - name: Downloading artifacts
       uses: actions/download-artifact@v2
       with:
-        name: firefly-desktop-ubuntu-latest
+        name: firefly-desktop-ubuntu-18.04
         path: assets
 
     - name: Preparing release body