Add -Wl,--as-needed flag for all executable builds (project-chip#37821)

* build: Add -Wl,--as-needed flag for all executable builds

PR#33628 has added an explicit link to libatomic for all linux-based builds
to fix a build issue on mips. This results with a NEEDED record for
libatomic.so.1 even when it's not required. One situation when this happens
is building on arm64 with clang.

Signed-off-by: Maciej Grela <m.grela@samsung.com>

* gn: Restrict --as-needed to only Linux builds using clang

Signed-off-by: Maciej Grela <m.grela@samsung.com>

* typo

Signed-off-by: Maciej Grela <m.grela@samsung.com>

* gn: Blacklist instead of whitelist, include ios and explanatory comment

Signed-off-by: Maciej Grela <m.grela@samsung.com>

---------

Signed-off-by: Maciej Grela <m.grela@samsung.com>

Author: enkiusz

build/config/compiler/BUILD.gn

@@ -671,3 +671,10 @@ config("specs_default") {
     ldflags = cflags
   }
 }
+
+config("link_as_needed") {
+  # ld64.lld on clang used by Apple does not have a --as-needed option
+  if (current_os != "mac" && current_os != "ios") {
+    ldflags = [ "-Wl,--as-needed" ]
+  }
+}

build/config/defaults.gni

@@ -61,6 +61,10 @@ declare_args() {
   # Defaults configs for pie.
   default_configs_pie = [ "${build_root}/config/compiler:pie_default" ]
 
+  # Default configs for GNU ld --as-needed
+  default_configs_link_as_needed =
+      [ "${build_root}/config/compiler:link_as_needed" ]
+
   # Defaults configs for warnings.
   default_configs_warnings =
       [ "${build_root}/config/compiler:warnings_default" ]
@@ -124,3 +128,4 @@ default_configs += default_configs_extra
 
 executable_default_configs = []
 executable_default_configs += default_configs_pie
+executable_default_configs += default_configs_link_as_needed