Remove magma toolchain from BUILD.gn

Change-Id: I4de63843cd671e43e0950405efeb5412b601720d
diff --git a/BUILD.gn b/BUILD.gn
index 46a31cf..d803397 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -19,8 +19,6 @@
 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 # IN THE SOFTWARE.
 
-import("//magma/gnbuild/magma.gni")
-
 group("generate_include_files") {
   deps = [
     ":build_version_include_file",
@@ -153,12 +151,6 @@
 
 static_library("spirv-tools") {
   deps = [
-    ":spirv-tools_src($magma_shared_toolchain)",
-  ]
-}
-
-source_set("spirv-tools_src") {
-  deps = [
     ":spirv-deps",
   ]
   sources = [
@@ -198,12 +190,6 @@
 static_library("spirv-tools-opt") {
   deps = [
     ":spirv-tools",
-    ":spirv-tools-opt_src($magma_shared_toolchain)",
-  ]
-}
-
-source_set("spirv-tools-opt_src") {
-  deps = [
     ":spirv-deps",
   ]
   sources = [