Add a LibraryIncludeDirectory for library headers that should be passed with -isystem.

Author: alexrp

doc/configuration/items.md

@@ -10,6 +10,9 @@ are used by the Zig SDK:
   every C/C++ source file by way of Clang's `-include` flag.
 * `IncludeDirectory`: Header include directories passed to the compiler with the
   `-I` flag. Note that this applies to Zig as well, not just C/C++.
+* `LibraryIncludeDirectory`: Header include directories passed to the compiler
+  with the `-isystem` flag. Note that this applies to Zig as well, not just
+  C/C++.
 * `LibraryReference`: Native libraries that should be linked to. These can be
   either static or dynamic. For multi-platform projects, additions to this item
   should be conditioned on the value of `RuntimeIdentifier` (or similar).

src/sdk/ZigCompile.cs

@@ -66,6 +66,9 @@ public string Configuration
     [Required]
     public string LanguageStandard { get; set; } = null!;
 
+    [Required]
+    public ITaskItem[] LibraryIncludeDirectories { get; set; } = null!;
+
     [Required]
     public ITaskItem[] LibraryReferences { get; set; } = null!;
 
@@ -542,6 +545,9 @@ void TryAppendWarningSwitch(string name)
         builder.AppendSwitchIfNotNull("-I ", GetWorkingDirectory() ?? ".");
         builder.AppendSwitchIfNotNull("-I ", PublicIncludeDirectory);
 
+        foreach (var include in LibraryIncludeDirectories)
+            builder.AppendSwitchIfNotNull("-isystem ", include);
+
         foreach (var include in IncludeDirectories)
             builder.AppendSwitchIfNotNull("-I ", include);
 

src/sdk/build/Vezel.Zig.Sdk.Build.targets

@@ -57,6 +57,7 @@
                     FastMath="$(FastMath)"
                     IncludeDirectories="@(IncludeDirectory)"
                     LanguageStandard="$(LanguageStandard)"
+                    LibraryIncludeDirectories="@(LibraryIncludeDirectory)"
                     LibraryReferences="@(LibraryReference)"
                     LinkTimeOptimization="$(LinkTimeOptimization)"
                     MicrosoftExtensions="$(MicrosoftExtensions)"

src/sdk/build/Vezel.Zig.Sdk.Test.targets

@@ -33,6 +33,7 @@
                     FastMath="$(FastMath)"
                     IncludeDirectories="@(IncludeDirectory)"
                     LanguageStandard="$(LanguageStandard)"
+                    LibraryIncludeDirectories="@(LibraryIncludeDirectory)"
                     LibraryReferences="@(LibraryReference)"
                     LinkTimeOptimization="$(LinkTimeOptimization)"
                     MicrosoftExtensions="$(MicrosoftExtensions)"