Add explicit path for otool and nm on macOS.

Both binaries show up in the default macOS search path, but as minimal wrappers
around xcrun. By specifying the paths explicitly, we avoid calls to xcrun.

Bug: 971452
Change-Id: Ia852f4b9991fd548f3c83bc04fdda7389e44a72a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649223Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667153}

build/toolchain/mac/BUILD.gn

@@ -298,7 +298,14 @@ template("mac_toolchain") {
       tocname = dylib + ".TOC"
       temporary_tocname = dylib + ".tmp"
 
-      does_reexport_command = "[ ! -e \"$dylib\" -o ! -e \"$tocname\" ] || otool -l \"$dylib\" | grep -q LC_REEXPORT_DYLIB"
+      # Use explicit paths to binaries. The binaries present on the default
+      # search path in /usr/bin are thin wrappers around xcrun, which requires a
+      # full CommandLineTools or Xcode install, and still may not choose the
+      # appropriate binary if there are multiple installs.
+      otool = "$mac_bin_path" + "otool"
+      nm = "$mac_bin_path" + "nm"
+
+      does_reexport_command = "[ ! -e \"$dylib\" -o ! -e \"$tocname\" ] || $otool -l \"$dylib\" | grep -q LC_REEXPORT_DYLIB"
 
       link_command = "$linker_driver $ld -shared "
       if (is_component_build) {
@@ -308,7 +315,7 @@ template("mac_toolchain") {
       link_command += "{{ldflags}} -o \"$dylib\" -Wl,-filelist,\"$rspfile\" {{libs}} {{solibs}}"
 
       replace_command = "if ! cmp -s \"$temporary_tocname\" \"$tocname\"; then mv \"$temporary_tocname\" \"$tocname\""
-      extract_toc_command = "{ otool -l \"$dylib\" | grep LC_ID_DYLIB -A 5; nm -gP \"$dylib\" | cut -f1-2 -d' ' | grep -v U\$\$; true; }"
+      extract_toc_command = "{ $otool -l \"$dylib\" | grep LC_ID_DYLIB -A 5; $nm -gP \"$dylib\" | cut -f1-2 -d' ' | grep -v U\$\$; true; }"
 
       command = "$env_wrapper if $does_reexport_command ; then $link_command && $extract_toc_command > \"$tocname\"; else $link_command && $extract_toc_command > \"$temporary_tocname\" && $replace_command ; fi; fi"