Use sapi/cli/php to run tests for faster failure (#6931)

We always run test steps on azure, even if a previous step failed, because we
don't want a failure in one configuration to prevent testing of other
configurations. However, if building PHP fails in the first place, then we
currently end up testing the system PHP binary. This is not only useless, but
will also result in a test runner hang and cause the job to time out.

Avoid this by using sapi/cli/php instead of the installed php as the test
binary. If we fail to build, then it will not exist, and testing will fail
immediately.

azure/macos/test.yml

@@ -9,7 +9,7 @@ steps:
       export SKIP_IO_CAPTURE_TESTS=1
       export CI_NO_IPV6=1
       rm -rf junit.xml | true
-      /usr/local/bin/php run-tests.php -P -q \
+      sapi/cli/php run-tests.php -P -q \
           -j$(sysctl -n hw.ncpu) \
           -g FAIL,XFAIL,BORK,WARN,LEAK,XLEAK,SKIP \
           --offline \

azure/test.yml

@@ -17,7 +17,7 @@ steps:
       export SKIP_IO_CAPTURE_TESTS=1
       export MSAN_SYMBOLIZER_PATH=/usr/lib/llvm-6.0/bin/llvm-symbolizer
       rm -rf junit.xml | true
-      php run-tests.php -P -q \
+      sapi/cli/php run-tests.php -P -q \
           -j$(/usr/bin/nproc) \
           -g FAIL,XFAIL,BORK,WARN,LEAK,XLEAK,SKIP \
           --offline \