valgrind: build for the right MIPS ISA revision level

When Valgrind detects a 32-bit MIPS architecture, it forcibly adds
-march=mips32 to CFLAGS; when it detects a 64-bit MIPS architecture, it
forcibly adds -march=mips64. This causes Valgrind to be built always for
the first ISA revision level (R1), even when the user has configured
Buildroot for the second ISA revision level (R2).

Since R2 is backwards compatible with R1, you can run a Valgrind built
for R1 in an R2 core. This is why nobody noticed about this problem, or
at least nobody complained.

But, since (I hope) we will support R6 in Buildroot in the near future,
this problem will become very important because R6 is not backwards
compatible with R1 or R2, so building Valgrind for R1 when your target
is R6 will result in a non-working Valgrind.

Override the CFLAGS variable (which Valgrind appends to its CFLAGS) and
pass the right -march option, so they take precedence over Valgrind's
wrongfully detected value.

Signed-off-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/valgrind/valgrind.mk

@@ -13,6 +13,19 @@ VALGRIND_CONF_OPTS = --disable-tls
 VALGRIND_AUTORECONF = YES
 VALGRIND_INSTALL_STAGING = YES
 
+# When Valgrind detects a 32-bit MIPS architecture, it forcibly adds
+# -march=mips32 to CFLAGS; when it detects a 64-bit MIPS architecture,
+# it forcibly adds -march=mips64. This causes Valgrind to be built
+# always for the first ISA revision level (R1), even when the user has
+# configured Buildroot for the second ISA revision level (R2).
+#
+# Override the CFLAGS variable (which Valgrind appends to its CFLAGS)
+# and pass the right -march option, so they take precedence over
+# Valgrind's wrongfully detected value.
+ifeq ($(BR2_mips)$(BR2_mipsel)$(BR2_mips64)$(BR2_mips64el),y)
+VALGRIND_CONF_ENV += CFLAGS="$(TARGET_CFLAGS) -march=$(BR2_GCC_TARGET_ARCH)"
+endif
+
 # On ARM, Valgrind only supports ARMv7, and uses the arch part of the
 # host tuple to determine whether it's being built for ARMv7 or
 # not. Therefore, we adjust the host tuple to specify we're on