Update 1948-obsolete-const-method-handle for Java 11 toolchain

Explicitly choose Java 8 for source and target version in build script
generating code via ASM.

Bug: 131683177
Test: art/test/run-test --host 1948
Change-Id: Ibd2696779b66d70a723f0c2eef8a18e4d2b7d9ec
diff --git a/test/1948-obsolete-const-method-handle/util-src/build-classes b/test/1948-obsolete-const-method-handle/util-src/build-classes
index 1b2d79a..af22dd4 100755
--- a/test/1948-obsolete-const-method-handle/util-src/build-classes
+++ b/test/1948-obsolete-const-method-handle/util-src/build-classes
@@ -38,7 +38,7 @@
 fi
 
 # Build the initial class files.
-(cd "${SRC_PATH}" && javac -cp "${ASM_CLASSPATH}" -d "${BUILD_PATH}" Main.java art/*.java art/constmethodhandle/*.java) || fail "javac error"
+(cd "${SRC_PATH}" && javac -source 8 -target 8 -cp "${ASM_CLASSPATH}" -d "${BUILD_PATH}" Main.java art/*.java art/constmethodhandle/*.java) || fail "javac error"
 # Modify the class files using ASM
 (cd "${SCRIPT_PATH}" && java -cp "${ASM_CLASSPATH}:${BUILD_PATH}" art.constmethodhandle.TestGenerator "${BUILD_PATH}" "$D8") || fail "generator failure"
 # Remove the modification classes. We don't need nor want them for the actual test.