[GN] Don't rely on fuchsia gni files being present

Change-Id: I3b5619287c1622a0cf6700d51e83110d65d06d51
diff --git a/BUILD.gn b/BUILD.gn
index 1b5e0f6..c2c4a9c 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -26,19 +26,21 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-import("//build/package.gni")
+if (is_fuchsia) {
+  import("//build/package.gni")
 
-package("curl") {
-  deps = [
-    ":curl_bin",
-  ]
+  package("curl") {
+    deps = [
+      ":curl_bin",
+    ]
 
-  binaries = [
-    {
-      name = "curl"
-      shell = true
-    },
-  ]
+    binaries = [
+      {
+        name = "curl"
+        shell = true
+      },
+    ]
+  }
 }
 
 config("curl_config") {