sandbox: Rework how SDL is enabled / disabled

Given that we can use Kconfig logic directly to see if we have a program
available on the host or not, change from passing NO_SDL to instead
controlling CONFIG_SANDBOX_SDL in Kconfig directly. Introduce
CONFIG_HOST_HAS_SDL as the way to test for sdl2-config and default
CONFIG_SANDBOX_SDL on if we have that, or not.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index d02c663..add8847 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -30,7 +30,7 @@
           %CD:~0,2%\msys64\usr\bin\bash -lc "pacman --noconfirm --needed -Sy make gcc bison flex diffutils openssl-devel libgnutls-devel libutil-linux-devel"
         displayName: 'Install Toolchain'
       - script: |
-          echo make tools-only_defconfig tools-only NO_SDL=1 > build-tools.sh
+          echo make tools-only_defconfig tools-only > build-tools.sh
           %CD:~0,2%\msys64\usr\bin\bash -lc "bash build-tools.sh"
         displayName: 'Build Host Tools'
         env:
@@ -47,7 +47,7 @@
       - script: brew install make ossp-uuid
         displayName: Brew install dependencies
       - script: |
-          gmake tools-only_config tools-only NO_SDL=1 \
+          gmake tools-only_config tools-only \
             HOSTCFLAGS="-I/usr/local/opt/openssl@1.1/include" \
             HOSTLDFLAGS="-L/usr/local/opt/openssl@1.1/lib" \
             -j$(sysctl -n hw.logicalcpu)