Improved Makefile.android's readability a bit.

Review URL: https://codereview.chromium.org/770783003

Cr-Commit-Position: refs/heads/master@{#25586}

Makefile.android

@@ -38,12 +38,10 @@ HOST_OS = $(shell uname -s | sed -e 's/Linux/linux/;s/Darwin/mac/')
 ANDROID_NDK_HOST_ARCH ?= $(shell uname -m | sed -e 's/i[3456]86/x86/')
 ifeq ($(HOST_OS), linux)
   TOOLCHAIN_DIR = linux-$(ANDROID_NDK_HOST_ARCH)
+else ifeq ($(HOST_OS), mac)
+  TOOLCHAIN_DIR = darwin-$(ANDROID_NDK_HOST_ARCH)
 else
-  ifeq ($(HOST_OS), mac)
-    TOOLCHAIN_DIR = darwin-$(ANDROID_NDK_HOST_ARCH)
-  else
-    $(error Host platform "${HOST_OS}" is not supported)
-  endif
+  $(error Host platform "${HOST_OS}" is not supported)
 endif
 
 ifeq ($(ARCH), android_arm)
@@ -52,38 +50,29 @@ ifeq ($(ARCH), android_arm)
   TOOLCHAIN_ARCH = arm-linux-androideabi
   TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
   TOOLCHAIN_VER = 4.8
+else ifeq ($(ARCH), android_arm64)
+  DEFINES  = target_arch=arm64 v8_target_arch=arm64 android_target_arch=arm64 android_target_platform=L
+  TOOLCHAIN_ARCH = aarch64-linux-android
+  TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
+  TOOLCHAIN_VER = 4.9
+else ifeq ($(ARCH), android_mipsel)
+  DEFINES  = target_arch=mipsel v8_target_arch=mipsel android_target_platform=14
+  DEFINES += android_target_arch=mips mips_arch_variant=mips32r2
+  TOOLCHAIN_ARCH = mipsel-linux-android
+  TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
+  TOOLCHAIN_VER = 4.8
+else ifeq ($(ARCH), android_ia32)
+  DEFINES = target_arch=ia32 v8_target_arch=ia32 android_target_arch=x86 android_target_platform=14
+  TOOLCHAIN_ARCH = x86
+  TOOLCHAIN_PREFIX = i686-linux-android
+  TOOLCHAIN_VER = 4.8
+else ifeq ($(ARCH), android_x87)
+  DEFINES = target_arch=x87 v8_target_arch=x87 android_target_arch=x86 android_target_platform=14
+  TOOLCHAIN_ARCH = x86
+  TOOLCHAIN_PREFIX = i686-linux-android
+  TOOLCHAIN_VER = 4.8
 else
-  ifeq ($(ARCH), android_arm64)
-    DEFINES  = target_arch=arm64 v8_target_arch=arm64 android_target_arch=arm64 android_target_platform=L
-    TOOLCHAIN_ARCH = aarch64-linux-android
-    TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
-    TOOLCHAIN_VER = 4.9
-  else
-    ifeq ($(ARCH), android_mipsel)
-      DEFINES  = target_arch=mipsel v8_target_arch=mipsel android_target_platform=14
-      DEFINES += android_target_arch=mips mips_arch_variant=mips32r2
-      TOOLCHAIN_ARCH = mipsel-linux-android
-      TOOLCHAIN_PREFIX = $(TOOLCHAIN_ARCH)
-      TOOLCHAIN_VER = 4.8
-
-    else
-      ifeq ($(ARCH), android_ia32)
-        DEFINES = target_arch=ia32 v8_target_arch=ia32 android_target_arch=x86 android_target_platform=14
-        TOOLCHAIN_ARCH = x86
-        TOOLCHAIN_PREFIX = i686-linux-android
-        TOOLCHAIN_VER = 4.8
-      else
-        ifeq ($(ARCH), android_x87)
-          DEFINES = target_arch=x87 v8_target_arch=x87 android_target_arch=x86 android_target_platform=14
-          TOOLCHAIN_ARCH = x86
-          TOOLCHAIN_PREFIX = i686-linux-android
-          TOOLCHAIN_VER = 4.8
-	else
-          $(error Target architecture "${ARCH}" is not supported)
-        endif
-      endif
-    endif
-  endif
+  $(error Target architecture "${ARCH}" is not supported)
 endif
 
 TOOLCHAIN_PATH = \