Fix intermittent hie002 failure

hie002 is a performance test that used to fail unpredictably:

	max_bytes_used Decrease from x86_64-linux-deb9-debug baseline @ HEAD~2:
	    Expected    hie002 (normal) max_bytes_used: 1190923992.0 +/-20%
	    Lower bound hie002 (normal) max_bytes_used:    952739193
	    Upper bound hie002 (normal) max_bytes_used:   1429108791
	    Actual      hie002 (normal) max_bytes_used:    726270784
	    Deviation   hie002 (normal) max_bytes_used:        -39.0 %
	peak_megabytes_allocated Decrease from x86_64-linux-deb9-debug baseline @ HEAD~2:
	    Expected    hie002 (normal) peak_megabytes_allocated: 2538.0 +/-20%
	    Lower bound hie002 (normal) peak_megabytes_allocated:   2030
	    Upper bound hie002 (normal) peak_megabytes_allocated:   3046
	    Actual      hie002 (normal) peak_megabytes_allocated:   1587
	    Deviation   hie002 (normal) peak_megabytes_allocated:  -37.5 %
	*** unexpected stat test failure for hie002(normal)

'max_bytes_used' and 'peak_megabytes_allocated' are too unstable without careful
control of the runtime configuration. We fix this by using a more predictable
metric, 'bytes allocated'.

testsuite/tests/hiefile/should_compile/all.T

 test('hie001',       normal,                   compile, ['-fno-code -fwrite-ide-info -fvalidate-ide-info'])
-test('hie002',       collect_compiler_stats(), compile, ['-fno-code -fwrite-ide-info'])
+test('hie002',       collect_compiler_stats('bytes allocated',10),
+                                               compile, ['-fno-code -fwrite-ide-info'])
 test('hie003',       normal,                   compile, ['-fno-code -fwrite-ide-info -fvalidate-ide-info'])
 test('hie004',       normal,                   compile, ['-fno-code -fwrite-ide-info -fvalidate-ide-info'])
 test('hie005',       normal,                   compile, ['-fno-code -fwrite-ide-info -fvalidate-ide-info'])