r300g: Use PATH_MAX instead of limiting ourselves to 100 chars.

When built with Gentoo's package manager, the Mesa source directory
exists seven directories deep. The path to the .test file is too long
and is silently truncated, leading to a crash. Just use PATH_MAX.

Cc: 10.4, 10.5 <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.gentoo.org/show_bug.cgi?id=540970
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>

src/gallium/drivers/r300/compiler/tests/rc_test_helpers.c

@@ -28,6 +28,7 @@
  */
 
 #include <errno.h>
+#include <limits.h>
 #include <regex.h>
 #include <stdlib.h>
 #include <stdio.h>
@@ -528,7 +529,6 @@ void init_compiler(
 }
 
 #define MAX_LINE_LENGTH 100
-#define MAX_PATH_LENGTH 100
 
 unsigned load_program(
 	struct radeon_compiler *c,
@@ -536,14 +536,14 @@ unsigned load_program(
 	const char *filename)
 {
 	char line[MAX_LINE_LENGTH];
-	char path[MAX_PATH_LENGTH];
+	char path[PATH_MAX];
 	FILE *file;
 	unsigned *count;
 	char **string_store;
 	unsigned i = 0;
 
 	memset(line, 0, sizeof(line));
-	snprintf(path, MAX_PATH_LENGTH, TEST_PATH "/%s", filename);
+	snprintf(path, PATH_MAX, TEST_PATH "/%s", filename);
 	file = fopen(path, "r");
 	if (!file) {
 		return 0;