azure: Drop 32-bit MSYS2 build

As of 2020-05-17, 32-bit MSYS2 is no longer actively supported by
the upstream [1]. Let's drop the 32-bit Windows host tool build.

[1] https://www.msys2.org/news/#2020-05-17-32-bit-msys2-no-longer-actively-supported

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index 186f148..30403fb 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -14,27 +14,19 @@
     displayName: 'Ensure host tools build for Windows'
     pool:
       vmImage: $(windows_vm)
-    strategy:
-      matrix:
-        i686:
-          MSYS_DIR: msys32
-          BASE_REPO: msys2-ci-base-i686
-        x86_64:
-          MSYS_DIR: msys64
-          BASE_REPO: msys2-ci-base
     steps:
       - script: |
-          git clone https://github.com/msys2/$(BASE_REPO).git %CD:~0,2%\$(MSYS_DIR)
+          git clone https://github.com/msys2/msys2-ci-base.git %CD:~0,2%\msys64
         displayName: 'Install MSYS2'
       - script: |
-          %CD:~0,2%\$(MSYS_DIR)\usr\bin\bash -lc "pacman --noconfirm -Syyuu"
+          %CD:~0,2%\msys64\usr\bin\bash -lc "pacman --noconfirm -Syyuu"
         displayName: 'Update MSYS2'
       - script: |
-          %CD:~0,2%\$(MSYS_DIR)\usr\bin\bash -lc "pacman --noconfirm --needed -S make gcc bison diffutils openssl-devel"
+          %CD:~0,2%\msys64\usr\bin\bash -lc "pacman --noconfirm --needed -S make gcc bison diffutils openssl-devel"
         displayName: 'Install Toolchain'
       - script: |
           echo make tools-only_defconfig tools-only NO_SDL=1 > build-tools.sh
-          %CD:~0,2%\$(MSYS_DIR)\usr\bin\bash -lc "bash build-tools.sh"
+          %CD:~0,2%\msys64\usr\bin\bash -lc "bash build-tools.sh"
         displayName: 'Build Host Tools'
         env:
           # Tell MSYS2 we need a POSIX emulation layer