building for arm targets by default passes --target to clang, because it
assumes it's cross compiling (so passes --target as if the host is different,
instead of assuming default)

probably also works: removing this entirely. but to be safe, pass the alpine clang host triple
--
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -915,8 +915,8 @@ config("compiler_cpu_abi") {
     } else if (current_cpu == "arm") {
       if (is_clang && !is_android && !is_nacl &&
           !(is_chromeos_lacros && is_chromeos_device)) {
-        cflags += [ "--target=arm-linux-gnueabihf" ]
-        ldflags += [ "--target=arm-linux-gnueabihf" ]
+        cflags += [ "--target=armv7-alpine-linux-musleabihf" ]
+        ldflags += [ "--target=armv7-alpine-linux-musleabihf" ]
       }
       if (!is_nacl) {
         cflags += [
@@ -930,8 +930,8 @@ config("compiler_cpu_abi") {
     } else if (current_cpu == "arm64") {
       if (is_clang && !is_android && !is_nacl && !is_fuchsia &&
           !(is_chromeos_lacros && is_chromeos_device)) {
-        cflags += [ "--target=aarch64-linux-gnu" ]
-        ldflags += [ "--target=aarch64-linux-gnu" ]
+        cflags += [ "--target=aarch64-alpine-linux-musl" ]
+        ldflags += [ "--target=aarch64-alpine-linux-musl" ]
       }
       if (is_android) {
         # Outline atomics crash on Exynos 9810. http://crbug.com/1272795