build: remove explicit linker call to libm on macOS

/usr/lib/libm.tbd is available via libSystem.*.dylib and
reexports sanitizer symbols. When building for asan
this becomes an issue as the linker will resolve the symbols
from the system library rather from libclang_rt.*

For V8 that rely on specific version of these symbols
that get bundled as part of clang, for ex:
https://source.chromium.org/chromium/chromium/src/+/main:v8/src/heap/cppgc/platform.cc;l=93-97
accepting nullptr for shadow_offset in `asan_get_shadow_mapping`,
linking to system version that doesn't support this will lead to
a crash.

Clang driver eventually links with `-lSystem`
https://github.com/llvm/llvm-project/blob/e82f93890daefeb38fe2a22ee3db87a89948ec57/clang/lib/Driver/ToolChains/Darwin.cpp#L1628-L1631,
this is done after linking the sanitizer libraries which
ensures right order of resolution for the symbols.

PR-URL: #56901
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Shelley Vohr <shelley.vohr@gmail.com>

deps/brotli/unofficial.gni

@@ -25,7 +25,7 @@ template("brotli_gn_build") {
     } else if (target_os == "freebsd") {
       defines = [ "OS_FREEBSD" ]
     }
-    if (!is_win) {
+    if (is_linux) {
       libs = [ "m" ]
     }
     if (is_clang || !is_win) {

deps/uv/unofficial.gni

@@ -87,11 +87,11 @@ template("uv_gn_build") {
       ]
     }
     if (is_posix) {
-      libs = [ "m" ]
       ldflags = [ "-pthread" ]
     }
     if (is_linux) {
       libs += [
+        "m",
         "dl",
         "rt",
       ]