servo: Merge #15529 - style: unbreak bindgen on BSDs and Solaris (from jbeich:freebsd); r=emilio

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---
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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [x] These changes fix Firefox [bug 1339033](https://bugzilla.mozilla.org/show_bug.cgi?id=1339033)
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- [x] These changes do not require tests because Tier3 platforms support is incomplete

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Source-Repo: https://github.com/servo/servo
Source-Revision: 5d8870fda9702ed552f7b11f5f772647aa7a6ce1

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 104548fa39db149650233f0e549d797392ed6664

servo/components/style/build_gecko.rs

@@ -136,6 +136,16 @@ mod bindings {
             }
             if cfg!(target_os = "linux") {
                 builder = builder.clang_arg("-DOS_LINUX=1");
+            } else if cfg!(target_os = "solaris") {
+                builder = builder.clang_arg("-DOS_SOLARIS=1")
+            } else if cfg!(target_os = "dragonfly") {
+                builder = builder.clang_arg("-DOS_BSD=1").clang_arg("-DOS_DRAGONFLY=1")
+            } else if cfg!(target_os = "freebsd") {
+                builder = builder.clang_arg("-DOS_BSD=1").clang_arg("-DOS_FREEBSD=1")
+            } else if cfg!(target_os = "netbsd") {
+                builder = builder.clang_arg("-DOS_BSD=1").clang_arg("-DOS_NETBSD=1")
+            } else if cfg!(target_os = "openbsd") {
+                builder = builder.clang_arg("-DOS_BSD=1").clang_arg("-DOS_OPENBSD=1")
             } else if cfg!(target_os = "macos") {
                 builder = builder.clang_arg("-DOS_MACOSX=1")
                     .clang_arg("-stdlib=libc++")