themes-wordpress/blockbase/sass/blocks/_buttons-outline-style.scss

@import 'button-mixins';
.wp-block-button {
	&.wp-block-button__link,
	.wp-block-button__link {
	   	&:not(.has-background):not(.has-text-color) {
		   @include button-outline-hover-styles;
	   	}
   	}
}
.wp-block-file .wp-block-file__button {
   @include button-outline-hover-styles;
}	

.wp-block-search {
   	&.wp-block-search__button-inside .wp-block-search__inside-wrapper .wp-block-search__button,
   	.wp-block-search__button {
	   @include button-outline-hover-styles;
   	}
}

//NOTE: Double-classed to raise specificity above parent theme's outline hover styles
//as an alternative to !important.  Only needed for the editor.
.wp-block-button.wp-block-button.is-style-outline {
	&.wp-block-button__link,
	.wp-block-button__link {
	   &:not(.has-background):not(.has-text-color) {
		   &:hover,
		   &:focus,
		   &.has-focus {
			   color: var(--wp--custom--button--color--background);
			   background-color: var(--wp--custom--button--color--text);
		   	}
	   	}
   	}
}