support/scripts/gen-bootlin-toolchains: fix RISC-V 64-bit toolchain description

We now support both MMU-enabled and MMU-less RISC-V 64-bit
configurations. However, the Bootlin toolchain for RISC-V 64-bit only
supports MMU-enabled configurations, but the current logic in
toolchain/toolchain-external/toolchain-external-bootlin/ does not take
this into account, and allows selecting the Booltin toolchain for
MMU-less RISC-V 64-bit configurations.

To fix this, the gen-bootlin-toolchains script is modified to add the
BR2_USE_MMU dependency to the description of the RISC-V 64-bit
toolchain.

However, the BR2_USE_MMU dependency was also added for glibc and musl
toolchains unconditionally, so to avoid duplicating the dependency, we
now only add it only if not already present in the list of
dependencies for this toolchain.

This will allow to fix:

  http://autobuild.buildroot.net/results/d6aee9b275b1ec399aea59758ac8f69fdc5691fc/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

support/scripts/gen-bootlin-toolchains

@@ -159,7 +159,7 @@ arches = {
         'prefix': 'riscv32',
     },
     'riscv64-lp64d': {
-        'conditions': ['BR2_riscv', 'BR2_riscv_g', 'BR2_RISCV_64', 'BR2_RISCV_ABI_LP64D'],
+        'conditions': ['BR2_riscv', 'BR2_riscv_g', 'BR2_RISCV_64', 'BR2_RISCV_ABI_LP64D', 'BR2_USE_MMU'],
         'prefix': 'riscv64',
     },
     's390x-z13': {
@@ -312,13 +312,15 @@ class Toolchain:
                 selects.append("BR2_TOOLCHAIN_EXTERNAL_UCLIBC")
             elif frag.startswith("BR2_TOOLCHAIN_EXTERNAL_CUSTOM_GLIBC"):
                 # glibc needs mmu support
-                depends.append("BR2_USE_MMU")
+                if "BR2_USE_MMU" not in depends:
+                    depends.append("BR2_USE_MMU")
                 # glibc doesn't support static only configuration
                 depends.append("!BR2_STATIC_LIBS")
                 selects.append("BR2_TOOLCHAIN_EXTERNAL_GLIBC")
             elif frag.startswith("BR2_TOOLCHAIN_EXTERNAL_CUSTOM_MUSL"):
                 # musl needs mmu support
-                depends.append("BR2_USE_MMU")
+                if "BR2_USE_MMU" not in depends:
+                    depends.append("BR2_USE_MMU")
                 selects.append("BR2_TOOLCHAIN_EXTERNAL_MUSL")
 
             # gcc version