Rollup merge of rust-lang#68863 - pietroalbini:azure-macos-10.15, r=Mark-Simulacrum

ci: switch macOS builders to 10.15

Azure Pipelines is deprecating the macOS 10.13 image we're currently running, [and they plan to remove them](https://devblogs.microsoft.com/devops/removing-older-images-in-azure-pipelines-hosted-pools/) on March 23, 2020. This PR switches our macOS builders to macOS 10.15.

r? @Mark-Simulacrum

Author: Dylan-DPC

src/bootstrap/test.rs

@@ -1051,10 +1051,10 @@ impl Step for Compiletest {
         cmd.arg("--docck-python").arg(builder.python());
 
         if builder.config.build.ends_with("apple-darwin") {
-            // Force /usr/bin/python on macOS for LLDB tests because we're loading the
+            // Force /usr/bin/python3 on macOS for LLDB tests because we're loading the
             // LLDB plugin's compiled module which only works with the system python
             // (namely not Homebrew-installed python)
-            cmd.arg("--lldb-python").arg("/usr/bin/python");
+            cmd.arg("--lldb-python").arg("/usr/bin/python3");
         } else {
             cmd.arg("--lldb-python").arg(builder.python());
         }

src/ci/azure-pipelines/auto.yml

@@ -63,7 +63,7 @@ jobs:
 - job: macOS
   timeoutInMinutes: 600
   pool:
-    vmImage: macos-10.13
+    vmImage: macos-10.15
   steps:
   - template: steps/run.yml
   strategy:

src/ci/azure-pipelines/steps/run.yml

@@ -51,10 +51,6 @@ steps:
   displayName: Install clang
   condition: and(succeeded(), not(variables.SKIP_JOB))
 
-- bash: src/ci/scripts/switch-xcode.sh
-  displayName: Switch to Xcode 9.3
-  condition: and(succeeded(), not(variables.SKIP_JOB))
-
 - bash: src/ci/scripts/install-wix.sh
   displayName: Install wix
   condition: and(succeeded(), not(variables.SKIP_JOB))

src/ci/azure-pipelines/try.yml

@@ -25,7 +25,7 @@ jobs:
 # - job: macOS
 #   timeoutInMinutes: 600
 #   pool:
-#     vmImage: macos-10.13
+#     vmImage: macos-10.15
 #   steps:
 #   - template: steps/run.yml
 #   strategy:

src/ci/scripts/install-clang.sh

@@ -19,9 +19,7 @@ if isMacOS; then
     # native clang is configured to use the correct path, but our custom one
     # doesn't. This sets the SDKROOT environment variable to the SDK so that
     # our own clang can figure out the correct include path on its own.
-    if ! [[ -d "/usr/include" ]]; then
-        ciCommandSetEnv SDKROOT "$(xcrun --sdk macosx --show-sdk-path)"
-    fi
+    ciCommandSetEnv SDKROOT "$(xcrun --sdk macosx --show-sdk-path)"
 
     # Configure `AR` specifically so rustbuild doesn't try to infer it as
     # `clang-ar` by accident.