[mips] Disable compact branch generation

Bug: http://b/31317834

Clang generates invalid beqc compact branch instruction. Disable
compact branch generation until clang is updated to include r278824,
which fixes the issue.

Error:
/tmp/backtrace_test-6a4a4f.s:6603: Error: invalid operands
`beqc $zero,$1,$BB31_ 6' clang++.real: error: assembler command
failed with exit code 1 (use -v to see in vocation)

Test for mips and mips64: cd system/core/libbacktrace && mma
Change-Id: I0b0f189e126621dbadb317ba711993e45004348d

cc/config/mips64_device.go

@@ -78,6 +78,9 @@ var (
 		"mips64r6": []string{
 			"-mips64r6",
 			"-msynci",
+
+			// revert once clang picks up r278824
+			"-mcompact-branches=never",
 		},
 	}
 )

cc/config/mips_device.go

@@ -114,6 +114,9 @@ var (
 			"-mfp64",
 			"-mno-odd-spreg",
 			"-msynci",
+
+			// revert once clang picks up r278824
+			"-mcompact-branches=never",
 		},
 	}
 )