Friendly error message on apex_available and min_sdk_version checks

1) suggest a fix at the end of the message
2) add new lines around the dependency path so that they are visually
separated from rest of the error message

Bug: N/A
Test: m with an intentional break
error: bionic/apex/Android.bp:32:1: module "com.android.runtime" variant "android_common_com.android.runtime_image": "libutils_headers" requires "libsystem_headers" that doesn't list the APEX under 'apex_available'.

Dependency path:
           via tag apex.dependencyTag: { name:executable payload:true}
    -> crash_dump{os:android,image:,arch:arm_armv8-a,sdk:,apex:apex10000}
           via tag cc.libraryDependencyTag: { Kind:staticLibraryDependency Order:normalLibraryDependency wholeStatic:false reexportFlags:false explicitlyVersioned:false dataLib:false ndk:false staticUnwinder:false makeSuffix: skipApexAllowedDependenciesCheck:false excludeInApex:false}
    -> libtombstoned_client_static{os:android,image:,arch:arm_armv8-a,sdk:,link:static,apex:apex10000}
           via tag cc.libraryDependencyTag: { Kind:staticLibraryDependency Order:normalLibraryDependency wholeStatic:true reexportFlags:true explicitlyVersioned:false dataLib:false ndk:false staticUnwinder:false makeSuffix: skipApexAllowedDependenciesCheck:false excludeInApex:false}
    -> libcutils{os:android,image:,arch:arm_armv8-a,sdk:,link:static,asan:,apex:apex10000}
           via tag cc.libraryDependencyTag: { Kind:headerLibraryDependency Order:normalLibraryDependency wholeStatic:false reexportFlags:false explicitlyVersioned:false dataLib:false ndk:false staticUnwinder:false makeSuffix: skipApexAllowedDependenciesCheck:false excludeInApex:false}
    -> libutils_headers{os:android,image:,arch:arm_armv8-a,sdk:,asan:,apex:apex10000}
           via tag cc.libraryDependencyTag: { Kind:headerLibraryDependency Order:normalLibraryDependency wholeStatic:false reexportFlags:true explicitlyVersioned:false dataLib:false ndk:false staticUnwinder:false makeSuffix: skipApexAllowedDependenciesCheck:false excludeInApex:false}
    -> libsystem_headers{os:android,image:,arch:arm_armv8-a,sdk:,asan:,apex:apex10000}

Consider adding "com.android.runtime" to 'apex_available' property of "libsystem_headers"

Change-Id: I09f92c3086ea433780133a33ba0ad73baee6dc41
diff --git a/apex/apex.go b/apex/apex.go
index 662bbbd..65260cc 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -2246,8 +2246,10 @@
 		if to.AvailableFor(apexName) || baselineApexAvailable(apexName, toName) {
 			return true
 		}
-		ctx.ModuleErrorf("%q requires %q that doesn't list the APEX under 'apex_available'. Dependency path:%s",
-			fromName, toName, ctx.GetPathString(true))
+		ctx.ModuleErrorf("%q requires %q that doesn't list the APEX under 'apex_available'."+
+			"\n\nDependency path:%s\n\n"+
+			"Consider adding %q to 'apex_available' property of %q",
+			fromName, toName, ctx.GetPathString(true), apexName, toName)
 		// Visit this module's dependencies to check and report any issues with their availability.
 		return true
 	})