Rename ApexName to ApexVariationName

In preparation for reusing the same variation for multiple apexes,
rename ApexName to ApexVariationName.

Bug: 164216768
Test: all soong tests
Change-Id: I88f2c5b192ffa27acd38e01952d0cefd413222a0
diff --git a/cc/compiler.go b/cc/compiler.go
index d0b5b46..4a42d07 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -335,10 +335,10 @@
 		flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_RECOVERY__")
 	}
 
-	if ctx.apexName() != "" {
+	if ctx.apexVariationName() != "" {
 		flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_APEX__")
 		if Bool(compiler.Properties.Use_apex_name_macro) {
-			flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_APEX_"+makeDefineString(ctx.apexName())+"__")
+			flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_APEX_"+makeDefineString(ctx.apexVariationName())+"__")
 		}
 		if ctx.Device() {
 			flags.Global.CommonFlags = append(flags.Global.CommonFlags, "-D__ANDROID_SDK_VERSION__="+strconv.Itoa(ctx.apexSdkVersion()))