Add riscv64 linux tools download support

Author: bitsk

Diff for: internal/arduino/cores/tools.go

@@ -129,6 +129,7 @@ func (tr *ToolRelease) RuntimeProperties() *properties.Map {
 var (
 	regexpLinuxArm   = regexp.MustCompile("arm.*-linux-gnueabihf")
 	regexpLinuxArm64 = regexp.MustCompile("(aarch64|arm64)-linux-gnu")
+	regexpLinuxRiscv64 = regexp.MustCompile("riscv64-linux-gnu")
 	regexpLinux64    = regexp.MustCompile("x86_64-.*linux-gnu")
 	regexpLinux32    = regexp.MustCompile("i[3456]86-.*linux-gnu")
 	regexpWindows32  = regexp.MustCompile("i[3456]86-.*(mingw32|cygwin)")
@@ -151,6 +152,8 @@ func (f *Flavor) isExactMatchWith(osName, osArch string) bool {
 		return regexpLinuxArm.MatchString(f.OS)
 	case "linux,arm64":
 		return regexpLinuxArm64.MatchString(f.OS)
+	case "linux,riscv64":
+		return regexpLinuxRiscv64.MatchString(f.OS)
 	case "linux,amd64":
 		return regexpLinux64.MatchString(f.OS)
 	case "linux,386":

Diff for: internal/arduino/cores/tools_test.go

@@ -34,6 +34,7 @@ func TestFlavorCompatibility(t *testing.T) {
 	linuxArm := &os{"linux", "arm"}
 	linuxArmbe := &os{"linux", "armbe"}
 	linuxArm64 := &os{"linux", "arm64"}
+	linuxRiscv64 := &os{"linux", "riscv64"}
 	darwin32 := &os{"darwin", "386"}
 	darwin64 := &os{"darwin", "amd64"}
 	darwinArm64 := &os{"darwin", "arm64"}
@@ -47,6 +48,7 @@ func TestFlavorCompatibility(t *testing.T) {
 		linuxArm,
 		linuxArmbe,
 		linuxArm64,
+		linuxRiscv64,
 		darwin32,
 		darwin64,
 		darwinArm64,
@@ -82,6 +84,7 @@ func TestFlavorCompatibility(t *testing.T) {
 		{&Flavor{OS: "x86_64-pc-linux-gnu"}, []*os{linux64}, []*os{linux64}},
 		{&Flavor{OS: "aarch64-linux-gnu"}, []*os{linuxArm64}, []*os{linuxArm64}},
 		{&Flavor{OS: "arm64-linux-gnu"}, []*os{linuxArm64}, []*os{linuxArm64}},
+		{&Flavor{OS: "riscv64-linux-gnu"}, []*os{linuxRiscv64}, []*os{linuxRiscv64}},
 	}
 
 	checkCompatible := func(test *test, os *os) {