LUCENE-9928: speed up analysis/icu regeneration (#82)

The compilation of the library is slow, disable optimization as it doesn't speed up our usage of the gennorm2 tool.
Use better heuristic for make parallelism (tests.jvms rather than just hardcoded value of four).

Author: rmuir

gradle/generation/icu.gradle

@@ -200,7 +200,7 @@ configure(project(":lucene:analysis:icu")) {
         executable "tar"
         workingDir icuBuildDir
         args = [
-            "-zxvf",
+            "-zxf",
             icuSrcTgz
         ]
       }
@@ -210,6 +210,8 @@ configure(project(":lucene:analysis:icu")) {
         executable "sh"
 
         workingDir icuSrcDir
+        environment("CFLAGS", "-O0")
+        environment("CXXFLAGS", "-O0")
         args = [
             "configure",
             "--prefix=${icuSrcDir}",
@@ -221,7 +223,7 @@ configure(project(":lucene:analysis:icu")) {
         executable "make"
         workingDir icuSrcDir
         args = [
-            "-j4"
+            "-j${propertyOrDefault('tests.jvms', '4')}"
         ]
       }
 
@@ -300,4 +302,4 @@ configure(project(":lucene:core")) {
   }
 
   regenerate.dependsOn wrapWithPersistentChecksums(generateEmojiPropertiesInternal)
-}
+}