alloc: use jemalloc when building with musl

It turns out that musl's allocator is slow enough to cause a fairly
noticeable performance regression when ripgrep is built as a static
binary with musl. We fix this by using jemalloc when building with musl.

We continue to use the default system allocator in all other scenarios.
Namely, glibc's allocator doesn't noticeably regress performance compared
to jemalloc. But we could add more targets to this logic if other
system allocators (macOS, Windows) prove to be slow.

This wasn't necessary before because rustc recently stopped using jemalloc
by default.

Fixes #1268

1 files changed, 3 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index e93c41a8..d8c68d75 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -61,6 +61,9 @@ version = "2.32.0"
 default-features = false
 features = ["suggestions"]
 
+[target.'cfg(target_env = "musl")'.dependencies.jemallocator]
+version = "0.3.0"
+
 [build-dependencies]
 lazy_static = "1.1.0"