Remove clang: true

clang is the default compiler since Android nougat

Test: mma & verified it´s still build with clang

Change-Id: I4d251ac8b0365165653351e254991d4064c74dc4
Signed-off-by: Lennart Wieboldt <lennart.1997@gmx.de>

Android.bp

@@ -19,7 +19,6 @@ cc_library_static {
     name: "libc++_static",
     host_supported: true,
     vendor_available: true,
-    clang: true,
     srcs: [
         "src/algorithm.cpp",
         "src/any.cpp",
@@ -80,7 +79,6 @@ cc_library_shared {
         enabled: true,
         support_system_process: true,
     },
-    clang: true,
     whole_static_libs: ["libc++_static"],
     stl: "none",