compiler: Always dynamically link executables for Fuchsia.

Fuchsia only supports PIE executables, specifically ET_DYN.

https://fuchsia.dev/fuchsia-src/concepts/process/program_loading

Author: alexrp

src/Compilation/Config.zig

@@ -135,6 +135,7 @@ pub const ResolveError = error{
     LibCppRequiresLibC,
     LibUnwindRequiresLibC,
     TargetCannotDynamicLink,
+    TargetCannotStaticLinkExecutables,
     LibCRequiresDynamicLinking,
     SharedLibrariesRequireDynamicLinking,
     ExportMemoryAndDynamicIncompatible,
@@ -360,6 +361,10 @@ pub fn resolve(options: Options) ResolveError!Config {
             if (options.link_mode == .dynamic) return error.TargetCannotDynamicLink;
             break :b .static;
         }
+        if (target.os.tag == .fuchsia and options.output_mode == .Exe) {
+            if (options.link_mode == .static) return error.TargetCannotStaticLinkExecutables;
+            break :b .dynamic;
+        }
         if (explicitly_exe_or_dyn_lib and link_libc and
             (target_util.osRequiresLibC(target) or
                 // For these libcs, Zig can only provide dynamic libc when cross-compiling.

src/main.zig

@@ -4118,6 +4118,7 @@ fn createModule(
             error.LibCppRequiresLibC => fatal("libc++ requires linking libc", .{}),
             error.LibUnwindRequiresLibC => fatal("libunwind requires linking libc", .{}),
             error.TargetCannotDynamicLink => fatal("dynamic linking unavailable on the specified target", .{}),
+            error.TargetCannotStaticLinkExecutables => fatal("static linking of executables unavailable on the specified target", .{}),
             error.LibCRequiresDynamicLinking => fatal("libc of the specified target requires dynamic linking", .{}),
             error.SharedLibrariesRequireDynamicLinking => fatal("using shared libraries requires dynamic linking", .{}),
             error.ExportMemoryAndDynamicIncompatible => fatal("exporting memory is incompatible with dynamic linking", .{}),