Add musl libc submodule

Since musl is already incorporated into the build system (see for
example configure.ac, Makefile.in), this patch adds a submodule for
musl based on the current v1.2.2 release.
The GitHub Actions configurations have also been updated to include
the musl based toolchain.

Signed-off-by: Florian Hofhammer <florian.hofhammer@fhofhammer.de>

.github/workflows/build.yaml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       matrix:
         os:     [ubuntu-18.04, ubuntu-20.04]
-        mode:   [newlib, linux]
+        mode:   [newlib, linux, musl]
         target: [rv32gc-ilp32d, rv64gc-lp64d]
     steps:
       - uses: actions/checkout@v2
@@ -40,7 +40,14 @@ jobs:
         id:   toolchain-name-generator
         run: |
           if [[ "${{ matrix.target }}" == *"32"* ]]; then BITS=32; else BITS=64; fi
-          if [[ "${{ matrix.mode }}" == "linux" ]]; then MODE="glibc"; else MODE="elf"; fi
+          case "${{ matrix.mode }}" in
+            "linux")
+              MODE="glibc";;
+            "musl")
+              MODE="musl";;
+            *)
+              MODE="elf";;
+          esac
           echo ::set-output name=TOOLCHAIN_NAME::riscv$BITS-$MODE-${{ matrix.os }}-nightly
 
       - uses: actions/upload-artifact@v2

.github/workflows/nightly-release.yaml

@@ -49,7 +49,7 @@ jobs:
     strategy:
       matrix:
         os:     [ubuntu-18.04, ubuntu-20.04]
-        mode:   [newlib, linux]
+        mode:   [newlib, linux, musl]
         target: [rv32gc-ilp32d, rv64gc-lp64d]
     steps:
       - uses: actions/checkout@v2
@@ -75,7 +75,14 @@ jobs:
         id:   toolchain-name-generator
         run: |
           if [[ "${{ matrix.target }}" == *"32"* ]]; then BITS=32; else BITS=64; fi
-          if [[ "${{ matrix.mode }}" == "linux" ]]; then MODE="glibc"; else MODE="elf"; fi
+          case "${{ matrix.mode }}" in
+            "linux")
+              MODE="glibc";;
+            "musl")
+              MODE="musl";;
+            *)
+              MODE="elf";;
+          esac
           echo ::set-output name=TOOLCHAIN_NAME::riscv$BITS-$MODE-${{ matrix.os }}-nightly
 
       - uses: actions/upload-artifact@v2

.gitmodules

@@ -24,3 +24,7 @@
 [submodule "qemu"]
 	path = qemu
 	url = https://git.qemu.org/git/qemu.git
+[submodule "musl"]
+	path = musl
+	url = git://git.musl-libc.org/musl
+	branch = master

configure

@@ -3596,7 +3596,7 @@ fi
   with_musl_src=$with_musl_src
 
 else
-  with_musl_src="\$(srcdir)/riscv-musl"
+  with_musl_src="\$(srcdir)/musl"
 
 fi
 

configure.ac

@@ -219,7 +219,7 @@ AX_ARG_WITH_SRC(gcc, riscv-gcc)
 AX_ARG_WITH_SRC(binutils, riscv-binutils)
 AX_ARG_WITH_SRC(newlib, newlib)
 AX_ARG_WITH_SRC(glibc, glibc)
-AX_ARG_WITH_SRC(musl, riscv-musl)
+AX_ARG_WITH_SRC(musl, musl)
 AX_ARG_WITH_SRC(gdb, riscv-gdb)
 AX_ARG_WITH_SRC(qemu, qemu)
 

musl

@@ -0,0 +1 @@
+Subproject commit 85e0e3519655220688e757b9d5bfd314923548bd