Fix: message error '--build-tools=BUILD_TOOL_NAME'

[marcel-dias]

This PR fixes the message showed when lsif-java identifies more than one build tool.

It is now show '--build-tool=BUILD_TOOL_NAME'. instead of '--build-tools=BUILD_TOOL_NAME'

Below I'm sharing logs showing the wrong beharior.

lsif-java version: 0.6.4

Usage logs with wrong error message

coursier launch --jvm 8 com.sourcegraph:lsif-java_2.13:0.6.4 -- index
https://repo1.maven.org/maven2/com/sourcegraph/lsif-java_2.13/0.6.4/lsif-java_2.13-0.6.4.pom
  100.0% [##########] 3.2 KiB (5.9 KiB / s)
https://repo1.maven.org/maven2/com/sourcegraph/lsif-semanticdb/0.6.4/lsif-semanticdb-0.6.4.pom
  100.0% [##########] 2.2 KiB (16.8 KiB / s)
https://repo1.maven.org/maven2/com/sourcegraph/semanticdb-java/0.6.4/semanticdb-java-0.6.4.pom
  100.0% [##########] 1.8 KiB (15.1 KiB / s)
https://repo1.maven.org/maven2/com/sourcegraph/lsif-semanticdb/0.6.4/lsif-semanticdb-0.6.4.jar
  100.0% [##########] 110.2 KiB (437.3 KiB / s)
https://repo1.maven.org/maven2/com/sourcegraph/semanticdb-java/0.6.4/semanticdb-java-0.6.4.jar
  100.0% [##########] 592.0 KiB (1.3 MiB / s)
https://repo1.maven.org/maven2/com/sourcegraph/lsif-java_2.13/0.6.4/lsif-java_2.13-0.6.4.jar
  100.0% [##########] 5.6 MiB (6.4 MiB / s)
error: Multiple build tools detected: Gradle, sbt. To fix this problem, use the '--build-tools=BUILD_TOOL_NAME' flag to specify which build tool to run.

Usage logs with --build-tools=gradle

coursier launch --jvm 8 com.sourcegraph:lsif-java_2.13:0.6.4 -- index --build-tools=gradle
error: found argument '--build-tools' which wasn't expected, or isn't valid in this context.
	Did you mean '--build-tool'?

[Strum355]

Thanks for the fix! 🙂 🎉

[olafurpg]

@marcel-dias Thank you for this contribution!